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Take a deep dive into BlackSuit ransomware and explore its capabilities, deployment, and some current targets. Explore how Deep Instinct is able to detect and prevent BlackSuit from taking advantage of your data.

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Five weeks ago, the KADOKAWA corporation began to experience service outages affecting multiple websites. The outages spread to other operations and were identified as a <a href="https://www.bleepingcomputer.com/news/security/blacksuit-ransomware-gang-claims-attack-on-kadokawa-corporation/">ransomware attack</a> by the BlackSuit ransomware group. BlackSuit claimed responsibility and threatened the public release of stolen information on July 1st unless their ransom demands were met.&nbsp;&nbsp;BlackSuit's ransomware is very similar to the Royal ransomware strain, which itself is considered the successor to the notorious Conti group. This suggests potential connections or shared developers. This connection can be explained in more detail in some of our older material that has been published on the subject: we examined both <a href="https://info.deepinstinct.com/conti-leaks-cyber-threat-reports">Conti</a> and <a href="https://www.deepinstinct.com/blog/black-basta-ransomware-threat-emergence">BlackBasta</a>, a Conti offshoot.&nbsp;<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt360d20b0f113f264/6696f82b06a674d134c5a4ee/fig1-blacksuit-victims.png" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 1: BlackSuit ransomware victims</figcaption></div></figure>Based on our analysis, we found that Deep Instinct prevents&nbsp;all new Blacksuit Windows Ransomware samples with an eight-month-old brain. Across the industry, however, these samples have a much lower detection rate than earlier sample versions of BlackSuit. As demonstrated in the graph above, that lower detection rate matches the sudden growth of BlackSuit ransomware victims.&nbsp;The samples BlackSuit is using are well designed for infiltration of legacy systems. Let’s take a closer look.&nbsp;<h5>Latest samples analysis:</h5>Newer samples of BlackSuit’s code mainly added additional layers of complications like encoding strings and imported DLLs for Anti-Analysis. They also added a mandatory ID argument to bypass automatic emulation, making the new samples more evasive.&nbsp;<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt2084d114ec3f8209/6696f82b77a7809e9044a25f/fig2-strings-encryption.png" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 2: String decryption</figcaption></div></figure>For example, according to VirusTotal, even though old Blacksuit samples have a high detection rate, the new samples from recent months have a much lower detection rate, indicating significant changes.<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt5bed08ab64e581fe/6696f82cd0c0ef789ec561b6/fig3-VT-detection-rate.png" width="auto" height="auto" style="text-align: center;max-width: auto;width: auto;height: auto;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 3: Detection rate in VirusTotal of new Blacksuit samples when first submitted</figcaption></div></figure>One of the more impactful changes allowed the threat actor to mask the ransomware as a legitimate part of a known free antivirus, Qihoo 360, including false watermarking. This masking has drastically lowered detection. The ransomware is hidden deep inside the legitimate looking application and only has to be executed with a token in the command line to operate as a ransomware.&nbsp;<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blteae79a1729b07bfd/6696f82c77a780582d44a263/fig4-embedded-legitimate-urls.png" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 4: Embedded URLs</figcaption></div></figure><figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt4e96f1780d57f20a/6696f82c6c1019fd6f39795e/fig5-fake-metadata.png" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 5: Fake Metadata</figcaption></div></figure>The masquerade file is not signed, indicating this is not the real Qihoo application. The functionality post infiltration remained the same as the other new samples, including the same mutex used.&nbsp;<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt3971600a651708d4/6696f82c79f2042205390cf0/fig6-VT-detectio-rate-stealthy-sample.png" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 6: VirusTotal detection rate.</figcaption></div></figure>

The main portion of the executable is nearly identical to Qihoo's real QHAccount.exe file, resulting in security software evasion.<figure><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img alt="image003.jpg" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt5dac21065b6f0d02/66990ac7d316c70da3b3419f/image003.jpg" height="auto" /><figcaption style="text-align: center;" style="text-align: center;">Figure 7: Side by side comparison of BlackSuit and Qihoo executables</figcaption></div></figure>Disclaimer: The official Qihoo 360 is not in any way involved with BlackSuit. The masking is the work of bad actors assuming Qihoo’s identity.&nbsp;<h5>Behaviors:</h5>The common behavior shared with all Windows samples didn’t change much and the main functionality remained the same, though some commands have changed:<table><tbody><tr><td>-p&nbsp;</td><td>Specifies the target directory where the ransomware will encrypt files&nbsp;</td></tr><tr><td>-killvm&nbsp;</td><td>Terminates the virtual machine (VM), preventing analysis&nbsp;</td></tr><tr><td>-allfilesEncrypt&nbsp;</td><td>Encrypts all accessible files, maximizing damage&nbsp;</td></tr><tr><td>-networkEncrypt&nbsp;</td><td>Encrypts files on connected network drives, spreading the attack&nbsp;</td></tr><tr><td>-localEncrypt&nbsp;</td><td>Restricts encryption to the local machine storage, limiting immediate impact&nbsp;</td></tr><tr><td>-percentEncrypt&nbsp;</td><td>Encrypts a specified percentage of files, potentially increasing performance&nbsp;</td></tr><tr><td>-demonoff&nbsp;</td><td>Operates in stealth mode, making detection harder&nbsp;</td></tr><tr><td>-list {file}&nbsp;</td><td>A targeted list of files to be included in the encryption process&nbsp;</td></tr><tr><td>-delete&nbsp;</td><td>The ransomware deletes itself after execution, hindering investigation&nbsp;</td></tr><tr><td>-thrcount {number}&nbsp;</td><td>Specifies the number of threads used for encryption, impacting both performance and resource usage.&nbsp;</td></tr><tr><td>-skip {file}&nbsp;</td><td>A list of files to be excluded from encryption&nbsp;</td></tr><tr><td>-noprotect&nbsp;</td><td>Disables self-protection mechanisms, allowing termination of the ransomware&nbsp;</td></tr></tbody></table>&nbsp;The new samples have encoded strings to complicate analysis, and need to be supplied with -id &lt;32 characters&gt;. They can also receive additional instructions, such as:&nbsp;&nbsp;<table><tbody><tr><td>-ep&nbsp;</td><td>(like the previous percentEncrypt) sets a percentage of each file that will be encrypted. Partial encryption&nbsp;</td></tr><tr><td>-path&nbsp;</td><td>Specific directory to encrypt&nbsp;</td></tr><tr><td>-localonly&nbsp;</td><td>(an addition to the previous networkEncrypt) without network drives&nbsp;</td></tr><tr><td>-networkonly&nbsp;</td><td>(an addition to the previous networkEncrypt) without local files&nbsp;</td></tr><tr><td>-aavm&nbsp;</td><td>(like the previous allfilesEncrypt) encrypts everything&nbsp;</td></tr></tbody></table>&nbsp;BlackSuit ransomware also boasts a few other functionalities:&nbsp;<ul><li>Initiates Asymmetric Key Exchange to get the secret encryption key.&nbsp;</li></ul><ul><li>Deletes shadow copies, in order to disable easy local restore:&nbsp;</li></ul><ul><ul><li>vssadmin delete shadow /all /quiet&nbsp;&nbsp;</li></ul></ul><ul><li>Encrypts&nbsp;</li></ul><ul><ul><li>Appends .blacksuit to the encrypted files&nbsp;</li></ul></ul><ul><li>Skips:&nbsp;</li></ul><ul><ul><li>Various file types like executables, drivers, and installers to avoid breaking the system.&nbsp;</li></ul></ul><ul><ul><li>Already encrypted files and the ransom note.&nbsp;</li></ul></ul><ul><li>Eventually, BlackSuit’s ransomware is capable of disabling safe mode and shutting down the system:&nbsp;</li></ul><ul><ul><li>bcdedit /deletevalue {current} safeboot&nbsp;&nbsp;</li></ul></ul><ul><ul><li>shutdown /r /t 0&nbsp;</li></ul></ul><ul><li>Drops ransom note: Usually named readme.blacksuit.txt. The content text is encrypted to avoid signature detection for the ransom note. The note includes a link for communication with the threat actor for ransom negotiations.</li></ul><figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt771fca19a69b58a1" alt="fig7-ransom-note.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt771fca19a69b58a1/6696f82de13bf8b63bf84456/fig7-ransom-note.png" width="auto" height="128" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 8: BlackSuit’s ransom note</figcaption></div></figure><h5>Infection chain</h5>The common initial attack vectors are RDP (possibly with stolen credentials), VPN and firewall vulnerabilities, Office email attachments (Macros), Torrent websites, Malicious ads, and various 3rd-party trojans. And the attackers have also used tools like CobaltStrike, WinRAR, PUTTY, Rclone, Advanced IP Scanner, Mimikatz, and GMER. The variety of attack vectors opens the possibility for infection across a much broader target group, endangering large amounts of data.&nbsp;<h5>Leak and news site</h5>The BlackSuit group operates a news and leak site on the DarkWeb that includes all the known victims of the threat actors. Once the timer for the ransom payment ends, the exfiltrated data is published.&nbsp;Alleged victims of BlackSuit ransomware have their data published under a profile featuring key information about their organization, including industry, number of employees, revenue, and contact information.<figure><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img alt="Figure 8: An example of an alleged victim's profile on BlackSuit's leak site " src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt6451cbdff41a7b39/6697d044d0c0efef3ec5697e/fig9-darkweb-leak_redact_WB.png" width="auto" height="auto" style="width: auto; height: auto;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 9: An example of a victim profile on BlackSuit's leak site</figcaption></div></figure><a href="https://info.deepinstinct.com/request-a-demo">Request a demo</a> to see how Deep Instinct can protect you from BlackSuit ransomware.&nbsp;Explore the BlackSuit IOCs below.<h5>IOCs</h5>f1684fb118d4d8fc56653fcc49e12a659b64c4459ba037fa94f21783235cc6ba&nbsp;dede96fd44c0f78eb79ceb63b898874e8922efc59d8bfb9f86505b1992bc00a3&nbsp; 6a2e454942cfeebb1140e1a28cb05fd49461d07792e97663378399c719fbc9ee&nbsp;79ab73a0e9dd8eac045c00fd1bd172a7f359588901f93c83e6740157eb21e7df&nbsp;7f09c2e35783fca69f0e12f31d767cecf8a98567f2b6f1e2d81d2b2e93fe6307&nbsp;60a9785ec20ec08b6792e304fc4b363abd54b8a7a2945dca9f97ee07783c4759&nbsp;5aeaa5c4f4100b2084814be72a695a5bf4a95fdb8a0c65704523608baa79b726&nbsp;d96ff4b3e188f7ff96ed28c1381a6318dd76bb1fbd6ca02c6ab0236e1c7f35aa&nbsp;3be3a3c2c1abc1d401e845a2b8952f4f3e55b510f3d6c1eb2a4503c7be09bec1&nbsp;90ae0c693f6ffd6dc5bb2d5a5ef078629c3d77f874b2d2ebd9e109d8ca049f2c&nbsp;6ad8215bd6b52d897dcfa0a9829720d0532adc741460ecb4b8f00c4427b6141c&nbsp;8605dec4ae4bd9f51297d1f244d0647bc0637d6ce6a957a5f810c64ae63276cb&nbsp; 2adcf43d221de2f72ba5088dac3a3193219412882df711d095f04e3f5b40767c&nbsp;&nbsp;readme.blacksuit.txt&nbsp;.blacksuit&nbsp;vssadmin delete shadows /all /quiet&nbsp;Mutex: WLm87eV1oNRx6P3E4Cy9&nbsp;

Deep Dive: Exposing Stealthy New BlackSuit Ransomware

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Uncorking Old Wine: Zero-Day from 2017 + Cobalt Strike Loader in Unholy Alliance

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DarkBeatC2: The Latest MuddyWater Attack Framework

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<h5>Key Takeaways</h5><ul><li>"UAC-0099" is a threat actor that has targeted Ukraine since mid-2022</li><li>Deep Instinct Threat Lab has identified new attacks by the threat actor</li><li>The threat actor was observed leveraging CVE-2023-38831</li><li>The threat actor targets Ukrainian employees working for companies outside of Ukraine</li></ul><h5>Introduction</h5>In May 2023, the Ukrainian CERT published advisory <a href="https://cert.gov.ua/article/4818341" target="_blank">#6710</a> about a threat actor dubbed “UAC-0099.” The advisory briefly details the threat actor’s activities and tools.Since the CERT-UA publication in May, Deep Instinct has identified new attacks carried out by “UAC-0099” against Ukrainian targets.This blog post will shed additional light on the threat group’s recent attacks, which feature common tactics, techniques, and procedures (TTPs), including the use of a fabricated court summons to bait targets in Ukraine into executing the malicious files.Important note: Some of the C2 servers related to these attacks are still active at the time of publication.<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt08d3b2f2d7d67bbf" alt="fig1-Attack-flow.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt08d3b2f2d7d67bbf/65835d869fa6cf660e286cfd/fig1-Attack-flow.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 1: Overview of recent UAC-0099 activities.</figcaption></div></figure><h5>RAR SFX with LNK Infection Vector</h5>In early August, “UAC-0099” sent an email impersonating the Lviv city court using the ukr.net email service.The email was sent to a corporate email box of a Ukrainian employee working remotely for a company outside of the Ukraine.The attached is an executable file created by WinRAR, the Windows-based file archiver and compression utility that can compress a file as a self-extracting archive (SFX):<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt8c3feebcf5b30766" alt="fig2-SFX-Execution.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt8c3feebcf5b30766/65835d85c3fb27179c19bffe/fig2-SFX-Execution.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 2: Prompt when executing the attached SFX file.</figcaption></div></figure>After extracting the contents of the archive, a new file is created with a double extension, in this case docx.lnk:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt52f1063996d6c6ac" alt="fig3-Double-extention-trick.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt52f1063996d6c6ac/65835d853ea3614ddc574a88/fig3-Double-extention-trick.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 3: Double extension social engineering trick.</figcaption></div></figure>The file looks like a regular document file. However, it’s a LNK shortcut disguised as a DOCX file. Closer inspection reveals that the file uses the “WordPad” application icon instead of a DOCX icon. When opened, the specially crafted LNK file executes PowerShell with malicious content:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="bltdd7e45750fbc5e70" alt="fig4-Malicious-powershhell_wz.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltdd7e45750fbc5e70/65835d8671a55d4766cd1dea/fig4-Malicious-powershhell_wz.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 4: Malicious PowerShell commands inside the LNK file.</figcaption></div></figure>The malicious PowerShell code decodes two base64 blobs and writes the output into VBS and DOCX files. After that, the PowerShell code opens the DOCX file as a decoy while also creating a new scheduled task that executes the VBS file every three minutes.The VBS malware was named “LonePage” by CERT-UA. When executed, it creates a hidden PowerShell process that communicates with a hardcoded C2 URL to fetch a text file. The rest of the PowerShell code is executed only if the response from the C2 is greater than one byte. In that instance, the PowerShell script checks to see if the string “get-content“ is included in the text file. If the string is present, then the script executes the code from the server and saves it as an array of bytes. If the string is absent, the script executes a combination of commands inside the text file from the server and some hard-coded basic enumeration commands such as “whoami:”<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt45c12455f8d2218f" alt="fig5-LonePage-VBS.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt45c12455f8d2218f/65835d85b782f0f0c55838b3/fig5-LonePage-VBS.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 5: LonePage VBS script.</figcaption></div></figure>Regardless of the C2 response, the results of executing the commands inside the txt file or the hardcoded commands are sent back to the same C2 server. However, it is sent to a different port via HTTP POST method.The DOCX document is a decoy to trick the victim into thinking they’re opening a legitimate DOCX file containing a court summons instead of a malicious file:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="bltf72caabeacbb69dc" alt="fig6-DOCX-Content.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltf72caabeacbb69dc/65835d86b0fbcbc10f626012/fig6-DOCX-Content.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 6: Contents of DOCX file.</figcaption></div></figure>In early November, another instance of this campaign was <a href="https://pastebin.com/rpFYCNPS" target="_blank">observed</a> using a different C2 address — 196.196.156[.]2.Since the threat actor controls the content of the “upgrade.txt” files, they can change it according to their objectives. As such, the content is not always the same and can vary.The following code was <a href="https://www.virustotal.com/gui/file/124c805af0ad7388f78fd0d048e4fadbc3217a897012615eb7aff7034d205c0b" target="_blank">observed</a> as a response from the C2 server at 2023-11-08 14:50:30 UTC.<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt9bd8ef7a5cd0ea04" alt="fig7-GetScreen-Command.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt9bd8ef7a5cd0ea04/65835d981f8952d579911826/fig7-GetScreen-Command.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 7: C2 Get-Screenshot command.</figcaption></div></figure>This PowerShell code is responsible for taking a screenshot. As mentioned above, the LonePage VBS sends the results back to the C2, allowing the threat actor to execute any PowerShell code on the infected computer and receive the response back.At the end of November 2023, another campaign instance was observed using the C2 address 2.59.222[.]98. In this case, the payload response from the C2 server aligns with what was described as “recon” activity in the <a href="https://web.archive.org/web/20231108142010/https:/pastebin.com/rpFYCNPS" target="_blank">pastebin</a>:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="bltfda9c4f87ac4975c" alt="fig8-Recon-Command.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltfda9c4f87ac4975c/65835d98be5d263767657a9a/fig8-Recon-Command.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 8: Recon commands received from C2 server.</figcaption></div></figure>The decoy document is a PDF file instead of a DOCX. And instead of the usual court summons document, the PDF file shows a smudged document:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt13277171b51512f1" alt="fig9-Smudged-decoy-PDF.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt13277171b51512f1/6583613d0543c5286e8f08c9/fig9-Smudged-decoy-PDF.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 9: Smudged decoy PDF document.</figcaption></div></figure><h5>HTA Infection Vector</h5>In contrast to the LNK attack vector described earlier, this attack uses HTA. The HTA method is similar, but there are notable differences. Instead of an LNK file invoking PowerShell, the HTA file includes HTML code that contains a VBScript that executes PowerShell. The scheduled task cadence is also different — it runs every four minutes instead of three in the previous cases.While CERT-UA reported in their advisory that the HTA file drops an HTML file as a decoy, Deep Instinct observed a similar court summons DOCX decoy document, like what was observed in the LNK chain.<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blt1289482c7f012b60" alt="fig10-HTA-content.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt1289482c7f012b60/65835d984135c46e76567bc0/fig10-HTA-content.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 10: HTA file content.</figcaption></div></figure><h5>CVE-2023-38831 Infection Vector</h5>In both attacks described below, “UAC-0099” exploited a known WinRAR vulnerability, <a href="https://www.group-ib.com/blog/cve-2023-38831-winrar-zero-day/" target="_blank">identified</a> by Group-IB and traced back to April 2023.The vulnerability stems from how WinRAR processes ZIP files. The exploitation requires a user to interact with a specially crafted ZIP archive.Here’s how it works: the attacker creates an archive with a benign filename with a space after the file extension — for example, “poc.pdf .” The archive includes a folder with the same name, including the space (something that is not possible under normal conditions, since the operating system does not allow the creation of a file with the same name). The folder includes an additional file with the same name as the benign file, including a space, followed by a “.cmd” extension.When a user opens a ZIP file containing these files in an unpatched version of WinRAR and double-clicks on the benign file, the file with the “cmd” extension is executed instead.The vulnerability might produce higher infection rates because the attacks are disguised so well; even security-savvy victims can fall for the deception. Expecting to open a benign file, the user will inadvertently execute malicious code.You can find a POC for the vulnerability in <a href="https://github.com/deepinstinct/UAC-0099-Targeting_UA" target="_blank">GitHub</a>. A patched WinRAR (version 6.23) was released on August 2, 2023.Deep Instinct identified two ZIP files created by “UAC-0099" on August 5, 2023:<figure style="text-align: center"><div data-img-caption-container="true" style="display: inline-block; text-align: center;"><img asset_uid="blte04762783408272b" alt="fig11-Malicious-cmd-inside-zip.png" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blte04762783408272b/65835d98b0fbcb3e03626016/fig11-Malicious-cmd-inside-zip.png" height="auto" style="text-align: center;" /><figcaption style="text-align: center;" style="text-align: center;">Figure 11: Contents of malicious “cmd” file inside ZIP archive.</figcaption></div></figure>The malicious “cmd” file is different in the two files, each containing a different C2 URI path.The modification time between the two files is only two seconds, indicating that, most likely, the files were created in an automated fashion. This, combined with the fact that UAC-0099 started to exploit the vulnerability several days after the patch, shows the level of sophistication of the attackers.While Google TAG <a href="https://blog.google/threat-analysis-group/government-backed-actors-exploiting-winrar-vulnerability/" target="_blank">identified</a> several Russian threat actors using the vulnerability to attack Ukrainian targets, the UAC-0099 activity is absent in their blog.The CVE assignment and the Group-IB blog about the vulnerability were published after “UAC-0099” leveraged the attack technique, indicating they likely knew how to exploit it.The decoy used in this campaign was once again the “summon to court” document theme.<h5>Conclusions and Recommendations</h5>The tactics used by “UAC-0099” are simple, yet effective. Despite the different initial infection vectors, the core infection is the same — they rely on PowerShell and the creation of a scheduled task that executes a VBS file.Monitoring and limiting the functionality of those components can reduce the risk of “UAC-0099” attacks — and/or identify them quickly in the event of compromise.The WinRAR exploitation is an interesting choice. Some people don’t update their software in a timely fashion, even with automatic updates. WinRAR requires a manual update, meaning that even if a patch is available, many people will likely still have a vulnerable version of WinRAR installed.Please make sure you have the <a href="https://www.rarlab.com/download.htm" target="_blank">latest</a> version of WinRAR installed.IOCs and the POC for the CVE-2023-38831 can be found on our <a href="https://github.com/deepinstinct/UAC-0099-Targeting_UA" target="_blank">GitHub</a>.<h5>IOCs</h5>147.78.46[.]40196.196.156[.]22.59.222[.]98<table style="width: 100%;"><thead class="bg-grey"><tr><th>SHA256</th><th>Description</th></tr></thead><tbody><tr><td>d21aa84542303ca70b59b53e9de9f092f9001f409158a9d46a5e8ce82ab60fb6</td><td>SFX</td></tr><tr><td>0eec5a7373b28a991831d9be1e30976ceb057e5b701e732372524f1a50255c7</td><td>LNK</td></tr><tr><td>8aca535047a3a38a57f80a64d9282ace7a33c54336cd08662409352c23507602</td><td>VBS</td></tr><tr><td>2c2fa6b9fbb6aa270ba0f49ebb361ebf7d36258e1bdfd825bc2faeb738c487ed</td><td>Decoy</td></tr><tr><td>659abb39eec218de66e2c1d917b22149ead7b743d3fe968ef840ef22318060fd</td><td>SFX</td></tr><tr><td>0aa794e54c19dbcd5425405e3678ab9bc98fb7ea787684afb962ee22a1c0ab51</td><td>LNK</td></tr><tr><td>4e8de351db362c519504509df309c7b58b891baf9cb99a3500b92fe0ef772924</td><td>VBS</td></tr><tr><td>53812d7bdaf5e8e5c1b99b4b9f3d8d3d7726d4c6c23a72fb109132d96ca725c2</td><td>Decoy</td></tr><tr><td>38b49818bb95108187fb4376e9537084062207f91310cdafcb9e4b7aa0d078f9</td><td>HTA</td></tr><tr><td>a10209c10bf373ed682a13dad4ff3aea95f0fdcd48b62168c6441a1c9f06be37</td><td>VBS</td></tr><tr><td>61a5b971a6b5f9c2b5e9a860c996569da30369ac67108d4b8a71f58311a6e1f1</td><td>Decoy</td></tr><tr><td>86549cf9c343d0533ef80be2f080a7e3c38c77a1dfbde0a2f89048127979ec2a</td><td>SFX</td></tr><tr><td>762c7289fb016bbcf976bd104bd8da72e17d6d81121a846cd40480dbdd876378</td><td>LNK</td></tr><tr><td>39d56eab8adfe9eb244914dde42ec7f12f48836d3ba56c479ab21bdbc41025fe</td><td>VBS</td></tr><tr><td>f75f1d4c561fcb013e262b3667982759f215ba7e714c43474755b72ed7f9d01e</td><td>Decoy</td></tr><tr><td>986694cad425c8f566e4e12c104811d4e8b30ce6c4c4d38f919b617b1aa66b05</td><td>CVE-2023-38831 ZIP</td></tr><tr><td>54458ebfbe56bc932e75d6d0a5c1222286218a8ef26face40f2a0c0ec2517584</td><td>CVE Payload</td></tr><tr><td>96ab977f8763762af26bad2b6c501185b25916775b4ed2d18ad66b4c38bd5f0d</td><td>VBS</td></tr><tr><td>6a638569f831990df48669ca81fec37c6da380dbaaa6432d4407985e809810da</td><td>Decoy</td></tr><tr><td>87291b918218e01cac58ea55472d809d8cdd79266c372aebe9ee593c0f4e3b77</td><td>CVE-2023-38831 ZIP</td></tr><tr><td>f5f269cf469bf9c9703fe0903cda100acbb4b3e13dbfef6b6ee87a907e5fcd1b</td><td>CVE Payload</td></tr><tr><td>e34fc4910458e9378ea357baf045e9c0c21515a0b8818a5b36daceb2af464ea0</td><td>VBS</td></tr><tr><td>2a3da413f9f0554148469ea715f2776ab40e86925fb68cc6279ffc00f4f410dd</td><td>SFX</td></tr><tr><td>0acd4a9ef18f3fd1ccf440879e768089d4dd2107e1ce19d2a17a59ebed8c7f5d</td><td>LNK</td></tr><tr><td>6f5f265110490158df91ca8ad429a96f8af69ca30b9e3b0d9c11d4fef74091e8</td><td>VBS</td></tr><tr><td>736c0128402d83cd3694a5f5bb02072d77385c587311274e3229e9b2fd5c5af7</td><td>Decoy</td></tr></tbody></table>

Threat Actor 'UAC-0099' Continues to Target Ukraine

blog-image-muddyc2go.jpg

The contents of this blog post were originally scheduled to be presented during an upcoming cybersecurity conference. However, interest in this topic has heightened due to the war in Israel and a suspected ongoing attack against Israeli targets. As such, we have decided to publish the relevant findings from the presentation now.<h5>Executive Summary:</h5><ul><li>Deep Instinct’s Threat Research team has identified a previously unreported C2 framework suspected to be in use by MuddyWater</li><li>The C2 framework may have been in use by the MuddyWater group since at least 2020</li><li>The framework’s web component is written in the Go programming language – hence the name we gave it: MuddyC2Go</li><li>MuddyWater seems to have stopped using PhonyC2 and is now using MuddyC2Go instead</li></ul><h5>Background</h5>In June 2023, we published a report about <a href="https://www.deepinstinct.com/blog/phonyc2-revealing-a-new-malicious-command-control-framework-by-muddywater" target="_self">PhonyC2</a>, a custom C2 framework used by the MuddyWater APT group.While analyzing previous PhonyC2 infrastructure, Deep Instinct uncovered anomalies that indicated MuddyWater might be using an additional C2 framework.At that time, we lacked sufficient evidence to support this claim. However, after we published our PhonyC2 research, we observed two IP addresses previously related to MuddyWater, one of those addresses which was hosting PhonyC2 had switched to a different C2 framework delivering a PowerShell payload.This behavior heightened suspicions of a new C2 framework. However, without seeing and observing the initial payload, those IP addresses could have been internal tests by MuddyWater before fully deploying the C2.Recently, Deep Instinct observed similar C2 activity on a different cluster of IP addresses that has not been associated previously with MuddyWater.This new activity’s initial payload confirmed our assessment that this activity is related to MuddyWater.<h5>Current MuddyWater Activity Using MuddyC2Go</h5><a href="https://www.deepinstinct.com/blog/new-muddywater-threat-old-kitten-new-tricks" target="_self">Previous research</a> has shown typical MuddyWater TTPs include spear-phishing emails containing archives or links to archives that include various legitimate remote administration tools.If the receiving target opens the file inside the archive, it installs a remote administration tool that allows the attacker to execute additional tools and malware, including MuddyWater’s PhonyC2.Deep Instinct observed the following changes in recent activity:<ul><li>The archives are now password protected. This is done to evade email security solutions that scan files inside archives without a password.</li><li>Instead of using a remote administration tool where an operator executes a PowerShell script to connect to MuddyWater’s C2, a new executable is now being sent. This executable contains an embedded PowerShell script that automatically connects to MuddyWater’s C2, eliminating the need for manual execution by the operator.</li></ul>Let’s examine several examples of this new C2 framework.<h5>July 2023 – Attack Against Jordanian Company</h5>Deep Instinct identified a file named “offtec.exe” which is an executable. Offtec is also the name of a Jordanian company.When executed, it runs a PowerShell script which connects to a MuddyC2Go server located at the IP address 45.150.64[.]239.The executable was built using PowerGUI from Quest Software. This tool allows the user to generate an executable that runs an embedded PowerShell script that is provided by the user.<figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 1: PowerGUI logo" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt2e55ad6e0e12cbe2/654af2a5b42e39040a69a428/fig1-PowerGUI-Logo.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 1: PowerGUI logo</figcaption></figure>After communicating with the C2, the communication is switched to dynamic DNS using the address “microsoftfice.ddns[.]net”The response from the C2 is again a PowerShell script that runs every 10 seconds and waits for commands from the operator using the C2:<figure style = "margin: auto; text-align: center;width: auto;"><img asset_uid="blt0f5f4af3edeedf94" alt="Figure 2: Part of the PowerShell code sent from the C2" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt0f5f4af3edeedf94/654af2a5b42e39040a69a424/fig2-Powershell-C2-Code.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 2: Part of the PowerShell code sent from the C2</figcaption></figure><h5>September 2023 – Attacks Against an Iraqi Telecommunications Provider</h5>In September, Deep Instinct identified additional variants of executables created with PowerGUI. The executables have been spread via password-protected RAR archives.The archives were uploaded from Iraq and their file name included the word “Korek.”<figure style = "margin: auto; text-align: center;width: auto;"><img asset_uid="bltaca79be7f5b4795d" alt="Figure 3: KorekPro file on VT" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltaca79be7f5b4795d/654af2a5b3460c040a0b095a/fig3-KorekPro-VT.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 3: KorekPro file on VT</figcaption></figure><a href="https://en.wikipedia.org/wiki/Korek_Telecom" target="_blank">Korek</a> is an Iraqi-Kurdish mobile phone operator. MuddyWater targeted Korek in <a href="https://mp-weixin-qq-com.translate.goog/s/NN_iRvwA6yOHFS9Z3A0RBA?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp" target="_blank">2019</a>.In this attack, the C2 IP addresses and dynamic DNS were different: ghostrider.serveirc[.]com<h5>October 2023 – “Swords of Iron” War</h5>While Iranian involvement in the war is still being investigated, on October 11, the fourth day of the war, Deep Instinct identified a scan of the MuddyC2Go URL from Israel in VirusTotal.Because the URL is unique and responded with PowerShell, it likely indicates there was a recent attack against an Israeli target by MuddyWater. This is also supported by our recent discovery of <a href="https://www.deepinstinct.com/blog/muddywater-en-able-spear-phishing-with-new-ttps" target="_self">another active campaign</a> from MuddyWater against Israeli targets.Deep Instinct could not identify an associated PowerGUI executable for this attack, although there could have been a different initial access vector to the attack that didn’t rely on social engineering.The C2 IP address that was used this time is 94.131.109[.]65.<h5>Attribution</h5>While investigating the PhonyC2 framework (written in Python) and its infrastructure, Deep Instinct identified servers responding with a generic “web.go” header. This header suggests MuddyWater is using a web application written in the Go programming language.In 2022, Mandiant <a href="https://www.mandiant.com/resources/blog/telegram-malware-iranian-espionage" target="_blank">reported</a> that MuddyWater wrote malware using Go, showing they are capable of using this language. However, the malware is “client-side,” whereas the C2 framework is “server-side.” As such, they are likely unrelated.Deep Instinct was able to find traces of a Go-based C2 framework used by MuddyWater dating back to the beginning of 2020.Deep Instinct identified 162.223.89[.]11 as the first IP address publicly attributed to MuddyWater using MuddyC2Go.Both <a href="https://www.secureworks.com/blog/business-as-usual-for-iranian-operations-despite-increased-tensions" target="_blank">SecureWorks</a> and <a href="https://blog.talosintelligence.com/iranian-apt-muddywater-targets-turkey/" target="_blank">Talos</a> reported a malicious Excel file (63e404011aeabb964ce63f467be29d678d0576bddb72124d491ab5565e1044cf) in January and February. When this file is opened, the malicious execution chain eventually leads to the C2 server 162.223.89[.]11.In May 2020, this IP address was <a href="https://www.virustotal.com/gui/url/dfe4269ae77af4ebd2f20156c7d1fb0eff05af17c25de4acadfda1b8f64e352f/details" target="_blank">observed</a> using MuddyC2Go.The IP address 109.201.140[.]103 has not been previously associated with MuddyWater. However, multiple scans from January, including one from Egypt, which aligns with MuddyWater’s interests and timeframe of above reports, contains unique URLs that are used by MuddyC2Go. Additionally, there is <a href="https://www.virustotal.com/gui/url/44b00e2d17de6df7ff6bcd27cff9f932e6c41052e3dce4603a55cbf41e153aca/details" target="_blank">scan</a> for a file named ssf.zip on this IP. Secure Sockets Funneling (SSF) was mentioned in the SecureWorks report as a tool used by MuddyWater.SSF is a tool that has been <a href="https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/seedworm-apt-iran-middle-east" target="_blank">reported</a> by multiple security vendors to be part of MuddyWater’s arsenal.In February 2022, CISA <a href="https://www.cisa.gov/news-events/cybersecurity-advisories/aa22-055a" target="_blank">published</a> indicators that signal MuddyWater activity, including the IP address 164.132.237[.]65.In March 2022, this address was <a href="https://www.virustotal.com/gui/url/39e38246cd33cd971ad6760207ad8faa7384536ef4a8cc487bcc4d4bc2d75390/details" target="_blank">observed</a> to be a MuddyC2Go server. It was previously <a href="https://www.security.ntt/blog/analysis-of-an-iranian-apts-e400-powgoop-variant" target="_blank">associated</a> with PowGoop.In April 2022, the IP address 141.95.177[.]130 was <a href="https://www.virustotal.com/gui/url/4a503712ccf32917b95fea40eb9d2ddc2f7c4e51552beb4cc179a6f1dd650f10/details" target="_blank">observed</a> hosting MuddyC2Go. Additionally, the passive DNS of this IP resolved to jbf1.nc1310022a[.]biz, a pattern that was already observed with PhonyC2 servers. A year later, in April 2023, Group-IB <a href="https://www.group-ib.com/blog/muddywater-infrastructure/" target="_blank">associated</a> this IP address to MuddyWater via a specific ETag header that was used in numerous MuddyWater servers.In the same report, Group-IB identified an LNK <a href="https://www.virustotal.com/gui/file/2528838a609aa143769efb37dff45af723868d4ed33eb1ce0e2d6ce64b2a1507/relations" target="_blank">file</a> from October 2022 that was communicating with the IP address 91.121.240[.]108. The <a href="https://www.virustotal.com/gui/url/c644ec1f939c1f072e7384ef6804f0a432f81b3c78acf8e0e9eedd44d6d0d55b/details" target="_blank">responses</a> from this IP indicate that it was MuddyC2Go. In addition, the LNK file was inside an archive named “request-for-service-no10102022.zip” The naming convention is very <a href="https://www.virustotal.com/gui/file/1670a59f573037142f417fb8c448a9022c8d31a6b2bf93ad77a9db2924b502af/details" target="_blank">similar</a> to the naming convention MuddyWater used in their <a href="https://www.deepinstinct.com/blog/new-muddywater-threat-old-kitten-new-tricks" target="_self">Syncro campaign</a>.Both Group-IB and Deep Instinct have <a href="https://www.deepinstinct.com/blog/phonyc2-revealing-a-new-malicious-command-control-framework-by-muddywater" target="_self">linked</a> the IP address 137.74.131[.]18 to MuddyWater. Deep Instinct initially observed PhonyC2 at this address, and after our publication, MuddyWater switched to MuddyC2Go on this IP address. Additionally, the IP address 137.74.131[.]20—which was previously reported by Group-IB —also started to host MuddyC2Go.<h5>Conclusion</h5>Due to the leak of PhonyC2 source code, MuddyWater stopped using the framework and switched to using a Go-based C2 framework. Since the actual source code of the new framework is not available, the full capabilities are unknown. However, based on past leaks and associated known activity, this is another framework that generates PowerShell payloads that MuddyWater uses in the “Actions on Objectives” phase in the “<a href="https://www.lockheedmartin.com/en-us/capabilities/cyber/cyber-kill-chain.html" target="_blank">Cyber Kill Chain</a>.” PowerShell has always been the bread and butter of MuddyWater operations.We recommend disabling PowerShell if it is not needed. If it is enabled, we recommend close monitoring of PowerShell activity.While it is not trivial to fingerprint the MuddyC2Go framework, as it looks like any other generic web application written in Go, Deep Instinct managed to identify previous attacks dating back to 2020 due to unique URL patterns generated by the framework.Currently, Deep Instinct has identified all known active MuddyC2Go servers hosted at “Stark Industries,” a VPS provider known to host malicious activity. Deep Instinct identified additional suspected MuddyC2Go servers hosted at Stark Industries without any malicious activity or known URL pattern.Additional IOCs and information regarding Iranian Threat Actors can be found in our <a href="https://github.com/deepinstinct/Israel-Cyber-Warfare-Threat-Actors" target="_blank">Git</a>.<h5>IOCs:</h5>Network<table style="width: 100%;"><thead class="bg-grey"><tr><th>IP Address</th><th>Description</th></tr></thead><tbody><tr><td>91.121.61[.]76</td><td>MuddyC2Go (2020)</td></tr><tr><td>109.201.140[.]103</td><td>MuddyC2Go (2020)</td></tr><tr><td>162.223.89[.]11</td><td>MuddyC2Go (2020)</td></tr><tr><td>164.132.237[.]65</td><td>MuddyC2Go (2022)</td></tr><tr><td>141.95.177[.]130</td><td>MuddyC2Go (2022) – (jbf1.nc1310022a[.]biz)</td></tr><tr><td>91.121.240[.]108</td><td>MuddyC2Go (2022)</td></tr><tr><td>137.74.131[.]18</td><td>MuddyC2Go (2023) – (qjk2.6nc051221c[.]co)</td></tr><tr><td>137.74.131[.]20</td><td>MuddyC2Go (2023)</td></tr><tr><td>45.150.64[.]239</td><td>MuddyC2Go (2023) – (microsoftfice.ddns[.]net)</td></tr><tr><td>95.164.46[.]35</td><td>MuddyC2Go (2023) – (ghostrider.serveirc[.]com)</td></tr><tr><td>45.67.230[.]91</td><td>MuddyC2Go (2023) – (Stark Industries)</td></tr><tr><td>94.131.109[.]65</td><td>MuddyC2Go (2023) – (Stark Industries)</td></tr><tr><td>95.164.46[.]199</td><td>MuddyC2Go (2023) – (Stark Industries</td></tr><tr><td>185.248.144[.]158</td><td>Suspected MuddyC2Go (2023) – (Stark Industries) – (mbcaction.hopto[.]org)</td></tr><tr><td>94.131.98[.]14</td><td>Suspected MuddyC2Go (2023) – (Stark Industries)</td></tr><tr><td>45.150.64[.]23</td><td>Suspected MuddyC2Go (2023) – (Stark Industries)</td></tr><tr><td>45.150.64[.]39</td><td>Suspected MuddyC2Go (2023) – (Stark Industries)</td></tr><tr><td>95.164.38[.]99</td><td>Suspected MuddyC2Go (2023) – (Stark Industries)</td></tr></tbody></table>File<table style="width: 100%;"><thead class="bg-grey"><tr><th>MD5</th><th>Description</th></tr></thead><tbody><tr><td>34212eb9e2af84eceb6a8234d28751b6</td><td>PowerShell response from 137.74.131[.]18</td></tr><tr><td>3c6486dfb691fc6642f1d35bdf247b90</td><td>PowerShell response from 137.74.131[.]18</td></tr><tr><td>55b99af81610eb65aabea796130a0462</td><td>PowerShell response from 137.74.131[.]18</td></tr><tr><td>d7ca8f3b5e21ed56abf32ac7cb158a7e</td><td>PowerShell response from 137.74.131[.]18</td></tr><tr><td>d3a2dee3bb8fcd8e8a0d404e7d1e6efb</td><td>PowerShell response from 137.74.131[.]20</td></tr><tr><td>4a70b1e4cb57c99502d89cdbbed48343</td><td>PowerShell response from 137.74.131[.]20</td></tr><tr><td>f08aa714fd59b68924843cbfddac4b15</td><td>PowerShell response from 137.74.131[.]20</td></tr><tr><td>db0e68d7d81f5c21e6e458445fd6e34b</td><td>offtec.exe (C2: 45.150.64[.]239)</td></tr><tr><td>dbcc0e9c1c6c1fff790caa0b2ffc2fe5</td><td>PowerShell script embedded in offtec.exe</td></tr><tr><td>e07adc4ee768126dc7c7339f4cb00120</td><td>PowerShell response from 45.150.64[.]239</td></tr><tr><td>feede05ba166a3c8668fe580a3399d8f</td><td>Performance.rar – Password protected archive</td></tr><tr><td>9894b84916f9264d897fe3b4a83bc608</td><td>KorekFile.rar – Password protected archive</td></tr><tr><td>9957250940377b39e405114f0a2fe84b</td><td>Performance/KorekFile.exe (C2: 95.164.46[.]35)</td></tr><tr><td>245c3ed373727c21ad9ee862b767e362</td><td>PowerShell script embedded in Performance/KorekFile</td></tr><tr><td>22971759adf816c6fb43104c0e1d89d6</td><td>PowerShell response from 95.164.46[.]35</td></tr><tr><td>5e0cc23a6406930a40696594021edb5f</td><td>KorekPro.rar – Password protected archive</td></tr><tr><td>79a638b2f2cc82bfe137f1d12534cda5</td><td>d.exe (C2: 95.164.46[.]35)</td></tr><tr><td>fc523904ca6e191eb2fdb254a6225577</td><td>PowerShell script embedded in d.exe</td></tr><tr><td>b867ec1cef6b1618a21853fb8cafd6e1</td><td>PowerShell response from 45.67.230[.]91</td></tr><tr><td>57641ce5af4482038c9ea27afcc087ee</td><td>PowerShell response from 94.131.109[.]65</td></tr><tr><td>fe5f94e5df19d95df26aaf774daad9df</td><td>PowerShell response from 95.164.46[.]199</td></tr></tbody></table>

MuddyC2Go – Latest C2 Framework Used by Iranian APT MuddyWater Spotted in Israel

MuddyWater Unleashed a New Social Engineering Campaign Against Israel During the Israel-Hamas War.

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<h5>Executive summary:</h5><ul><li>Deep Instinct’s Threat Research team has identified a new campaign from the “MuddyWater” group</li><li>The campaign has been observed attacking two Israeli targets</li><li>The campaign exhibits updated TTPs to previously reported MuddyWater activity</li></ul><figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 1: Campaign overview " src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt6790e59d9363b777/65426ffc4ed3b2001a90c710/fig1-muddywater-campaign-overview.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 1: Campaign overview</figcaption></figure><h5>Introduction</h5><a href="https://www.deepinstinct.com/blog/new-muddywater-threat-old-kitten-new-tricks" target="_self">Previous</a> research showed that MuddyWater has sent spear-phishing emails, starting back in 2020, with direct links, as well as PDF, RTF, and HTML attachments containing links to archives hosted on various file-sharing platforms.Those archives contained installers for various legitimate remote administration tools.Before launching the new campaign during the Israel-Hamas war, MuddyWater <a href="https://twitter.com/k3yp0d/status/1719269176101990574" target="_blank">reused</a> previously known remote administration tools, utilizing a new file-sharing service called “<a href="https://www.storyblok.com/" target="_blank">Storyblok</a>.”On October 30th Deep Instinct identified two archives hosted on “Storyblok” containing a new multi-stage infection vector. It contains hidden files, an LNK file that initiates the infection, and an executable file designed to unhide a decoy document while executing <a href="https://www.n-able.com/features/advanced-monitoring-agent" target="_blank">Advanced Monitoring Agent</a>, a remote administration tool.This is the first public report about MuddyWater utilizing this remote administration tool.<h5>The Multi-stage Social Engineering Campaign</h5>While Deep Instinct could not verify the spreading mechanism of the new campaign, it most likely starts with a spear-phishing email, similar to previous campaigns.The content of the email lures the victim into downloading an archive hosted at “a.storyblok[.]com”In this analysis, we examine the “defense-video.zip” file.When the archive is extracted, several folders must be navigated until a LNK shortcut, which looks like another folder named “Attachments,” is found:<figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 2: LNK Shortcut" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blte46c4bf1b082e1d5/65427050a67ffd001b94e1c9/fig2-muddywater-hidden-lnk-shortcut.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 2: LNK Shortcut</figcaption></figure>However, there are additional hidden folders and files extracted from the archive:<figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 3: Hidden folders" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltad15ce5115cba266/654270aa2149b10407ad84f5/fig3-muddywater-hidden-folders.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 3: Hidden folders</figcaption></figure>When the victim opens the LNK file, the infection chain starts.By examining the LNK file, we can see that it executes an executable from one of the hidden directories:<figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 4: LNK command line arguments" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt64dfe55de3f736ef/654270df7265fb04074f77da/fig4-muddywater-lnk-command-line-arguments.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 4: LNK command line arguments</figcaption></figure>The file “Diagnostic.exe” has been used in both archives Deep Instinct observed. The purpose of this file is to execute another executable called “Windows.Diagnostic.Document.EXE,” which is located in the hidden directory named “.end” under a “Windows.Diagnostic.Document” hidden directory.The file named “Windows.Diagnostic.Document.EXE” is a signed, legitimate installer for “Advanced Monitoring Agent.”In addition to executing the remote administration tool, “Diagnostic.exe” also opens a new Windows Explorer window of the hidden “Document” folder. This is done to fool the victim that opened the LNK file into thinking that it was indeed a folder.The decoy document is an official memo from the Israeli Civil Service Commission, which can be publicly downloaded from their <a href="https://www.gov.il/he/departments/news/disciplinary-treatment-statements-against-israel-wartime-news" target="_blank">website</a>.The memo describes what to do in case a government worker expresses opinions against the Israeli state on social networks:<figure style = "margin: auto; text-align: center;width: auto;"><img alt="Figure 5: Decoy document" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltc8cf7596101ee9db/654270fca184e7001b4f934b/fig5-muddywater-csc-decoy-document.png" height="auto" style="margin: auto;text-align: center;width: auto;" /><figcaption style = "text-align: center;" style="text-align: center;">Figure 5: Decoy document</figcaption></figure><h5>Conclusion</h5>MuddyWater continues to attack Israeli targets in various ongoing campaigns.In this campaign, MuddyWater employs updated TTPs. These include a new public hosting service, employing a LNK file to initiate the infection, and utilizing intermediate malware that mimics the opening of a directory while executing a new remote administration tool.After the victim has been infected, the MuddyWater operator will connect to the infected host using the legitimate remote administration tool and will start doing reconnaissance on the target.After the reconnaissance phase, the operator will likely execute PowerShell code which will cause the infected host to beacon to a custom C2 server.MuddyWater has used <a href="https://www.deepinstinct.com/blog/phonyc2-revealing-a-new-malicious-command-control-framework-by-muddywater" target="_self">PhonyC2</a> in the past. However, Deep Instinct recently observed MuddyWater using a new C2 framework named MuddyC2Go – a detailed blog will be published soon, stay tuned.<h5>IOCs:</h5>File<table style="width: 100%;"><thead class="bg-grey"><tr><th>MD5</th><th>Description</th></tr></thead><tbody><tr><td>37c3f5b3c814e2c014abc1210e8e69a2</td><td>Archive containing Atera Agent</td></tr><tr><td>16923d827a440161217fb66a04e8b40a</td><td>Atera Agent Installer</td></tr><tr><td>7568062ad4b22963f3930205d1a14df7</td><td>Archive containing Atera Agent</td></tr><tr><td>39eea24572c14910b67242a16e24b768</td><td>Archive containing Atera Agent</td></tr><tr><td>2e09e53135376258a03b7d793706b70f</td><td>Atera Agent Installer</td></tr><tr><td>1f0b9aed4b2c8d958a9b396852a62c9d</td><td>Archive containing SimpleHelp</td></tr><tr><td>065f0871b6025b8e61f35a188bca1d5c</td><td>SimpleHelp Installer</td></tr><tr><td>146cc3a1a68be349e70b79f9115c496b</td><td>defense-video.zip</td></tr><tr><td>dd247ccd7cc3a13e1c72bb01cf3a816d</td><td>Attachments.lnk</td></tr><tr><td>8d2199fa11c6a8d95c1c2b4add70373a</td><td>Diagnostic.exe</td></tr><tr><td>04afff1465a223a806774104b652a4f0</td><td>Advanced Monitoring Agent Installer</td></tr><tr><td>6167f03c8b2734c20eb02d406d3ba651</td><td>Decoy Document (defense-video.zip)</td></tr><tr><td>e8f3ecc0456fcbbb029b1c27dc1faad0</td><td>attachments.zip</td></tr><tr><td>952cc4e278051e349e870aa80babc755</td><td>Decoy Document (attachments.zip)</td></tr></tbody></table>Network<table style="width: 100%;"><thead class="bg-grey"><tr><th>IP or URL</th><th>Description</th></tr></thead><tbody><tr><td>ws.onehub[.]com/files/7f9dxtt6</td><td>URL to Archive of Atera Agent</td></tr><tr><td>a.storyblok[.]com/f/253959/x/b92ea48421/form.zip</td><td>URL to Archive of Atera Agent</td></tr><tr><td>a.storyblok[.]com/f/255988/x/5e0186f61d/questionnaire.zip</td><td>URL to Archive of Atera Agent</td></tr><tr><td>a.storyblok[.]com/f/259791/x/94f59e378f/questionnaire.zip</td><td>URL to Archive of SimpleHelp</td></tr><tr><td>146.70.149[.]61</td><td>MuddyWater’s SimpleHelp server</td></tr><tr><td>146.70.124[.]102</td><td><a href="https://twitter.com/MichalKoczwara/status/1719294254206288001" target="_blank">Suspected MuddyWater’s SimpleHelp server</a></td></tr><tr><td>37.120.237[.]204</td><td>Suspected MuddyWater’s SimpleHelp server</td></tr><tr><td>37.120.237[.]248</td><td>Suspected MuddyWater’s SimpleHelp server</td></tr><tr><td>a.storyblok[.]com/f/259837/x/21e6a04837/defense-video.zip</td><td>URL to Archive of Advanced Monitoring Agent</td></tr><tr><td>a.storyblok[.]com/f/259791/x/91e2f5fa2f/attachments.zip</td><td>URL to Archive of Advanced Monitoring Agent</td></tr></tbody></table>Additional IOCs regarding MuddyWater can be found in our GitHub page: <a href="https://github.com/deepinstinct/Israel-Cyber-Warfare-Threat-Actors" target="_blank">https://github.com/deepinstinct/Israel-Cyber-Warfare-Threat-Actors</a>

MuddyWater eN-Able spear-phishing with new TTPs

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PhonyC2: Revealing a New Malicious Command & Control Framework by MuddyWater

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Deep Instinct’s Threat Research Lab recently noticed a new strain of a JavaScript-based dropper that is delivering Bumblebee and IcedID. The dropper contains comments in Russian and employs the unique user-agent string “PindOS”, which may be a <a href="https://en.wikipedia.org/wiki/Anti-American_sentiment_in_Russia#Pindos" target="_blank">reference</a> to current (and past) anti-American sentiment in Russia.Bumblebee is a malware loader first discovered in March 2022. It was associated with <a href="https://info.deepinstinct.com/conti-leaks-cyber-threat-reports" target="_self">Conti group</a> and was being used as a replacement for BazarLoader. It acts as a primary vector for multiple types of other malware, including ransomware.IcedID is a modular banking malware designed to steal financial information. It has been seen in the wild since at least 2017 and has recently been <a href="https://www.bleepingcomputer.com/news/security/new-icedid-variants-shift-from-bank-fraud-to-malware-delivery/" target="_blank">observed</a> shifting some of its focus to malware delivery.<h5>Bumblebee’s Dilemma – PowerShell or JavaScript?</h5><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltac10f75989680347" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltac10f75989680347/6493347d48e15a005746c1ff/fig00-bumble_meme.jpg" style="text-align: center;"/></figure>Bumblebee’s primary modus operandi, including its most recent <a href="https://www.secureworks.com/blog/bumblebee-malware-distributed-via-trojanized-installer-downloads" target="_blank">major campaign</a>, involves a PowerShell-based first stage with very characteristic obfuscation (“elemXXX”). This serves as a wrapper and loading routine for an embedded 64-bit payload .DLL. Our analysis of this flow can be found <a href="/blog/the-dark-side-of-bumblebee-malware-loader" target="_self">here</a>.The possible switch to JavaScript instead of PowerShell marks a significant change in Bumblebee’s well-established TTP’s.<h5>IcedID – From Banker to Loader?</h5>As recent reports indicate, IcedID appears to be partially following in Emotet’s footsteps and may be abandoning its banking and financial functionalities in favor of becoming a more generalized loader-type malware. An association with a new JavaScript type of dropper can be seen as another step in this direction.<h5>PindOS JavaScript Technical Analysis</h5>Once de-obfuscated, the dropper is surprisingly simple. It consists of a single function, “exec,” which gets four parameters:<ul><li>“UserAgent” – The user-agent string to be used when downloading Bumblebee’s .DLL</li><li>“URL1” – First address to download from</li><li>“URL2” – Second address to download from</li><li>“RunDLL” – Payload .DLL exported function to call</li></ul>When executed, the dropper will attempt to download the payload initially from URL1 and execute it by calling on the specified export directly via rundll32.exe. If this fails, the dropper will attempt to download the payload from URL2 and execute it using a combination of PowerShell and rundll32.exe.The downloaded payload is saved to %appdata%/Microsoft/Templates/&lt;6-char-random-number&gt;.dat<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt310d8e627d3469ad" alt="Figure 1 – PindOS' main function" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt310d8e627d3469ad/6493347db9a076b80b92866c/fig01-pindos-main-function.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 1 – PindOS' main function</figcaption></figure>The function is then called twice, with four separate URLs:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt94b88382eb4426e4" alt="Figure 2 – exec function call from Bumblebee dropper" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt94b88382eb4426e4/6493347dd5b9a5988d6de2e6/fig02-exec-function-call-from-bumblebee-dropper.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 2 – exec function call from Bumblebee dropper</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt2ccea6ece70d6aef" alt="Figure 3 – exec function call from IcedID dropper" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt2ccea6ece70d6aef/6493347d1fb2d3643c496f99/fig03-exec-call-from-icedid-dropper.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 3 – exec function call from IcedID dropper</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltf4668bbd24eb05b8" alt="Figure 4 – Payload download" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltf4668bbd24eb05b8/6493347df7411b69d437e201/fig04-payload-download.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 4 – Payload download</figcaption></figure>The retrieved payloads are generated pseudo-randomly “on-demand” which results in a new sample hash each time a payload is fetched. This is commonly done to avoid signature-based detection. However, in Bumblebee’s case, this seems somewhat ineffective compared to the previous flow (which did not write the payload directly to disk), as the samples are fairly <a href="https://www.virustotal.com/gui/file/28c87170f2525fdecc4092fb347acd9b8350ed65e0fd584ce9fc001fd237d523/detection/f-28c87170f2525fdecc4092fb347acd9b8350ed65e0fd584ce9fc001fd237d523-1686560298" target="_blank">well detected</a> even on “first-seen”. This is likely due to the generated payload’s exports and several other indicators which remain constant and do not vary across the different generated samples.<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt9a6ab350a777b88a" alt="Figure 5 – A generalized comparison of Bumblebee’s infection flows - “older” on the right; “newer” on the left." src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt9a6ab350a777b88a/64933d2de66699a1d52eb992/fig05-a-generalized-comparison-of-bumblebees-infection-flows.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 5 – A generalized comparison of Bumblebee’s infection flows - “older” on the right; “newer” on the left.</figcaption></figure>According to Virus Total, on “first-seen” PindOS droppers have mostly received very low detection rates:<img asset_uid="blt5a182e8e00749668" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt5a182e8e00749668/64933d2d1fb2d36df6496fcb/fig06-vt-first-seen-detection-pindos-virus.png"/><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt6e2212907fb50273" alt="Figures 6 & 7 – VT first-seen detection for PindOS droppers" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt6e2212907fb50273/64933d2d48a8ff009c477fde/fig07-vt-first-seen-detection-pindos-dropper.png" style="text-align: center;"/><figcaption style="text-align: center;">Figures 6 &amp; 7 – VT first-seen detection for PindOS droppers</figcaption></figure><h5>Bumblebee DLL Payload Analysis Highlights</h5>The DLL payload is slightly different from the one previously encountered. Dynamically, it is very similar, with the addition of a few layers of obfuscation. It’s anti-debugging and anti-VM/sandbox features remain the same but with some additional “legitimate looking” strings taken from the <a href="https://github.com/FFmpeg/FFmpeg/blob/1617d1a752d5e97d5e74f6c384609c027c884553/libavutil/error.c" target="_blank">FFmpeg project open-source</a> project’s “error.c” file and a few other files from the same project added for distraction purposes:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt64d2e5ce682d4b38" alt="Figure 8 – Strings found in Bumblebee DLL" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt64d2e5ce682d4b38/6493347d9601bc69e508214d/fig08-strings-found-in-bumblebee-dll.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 8 – Strings found in Bumblebee DLL</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltff29e3f9d11aa98a" alt="Figure 9 – FFmpeg project source, “error.c” file." src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltff29e3f9d11aa98a/6493347dea50bc3ffabea7f4/fig09-ffmpeg-project-source-error.c-file.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 9 – FFmpeg project source, “error.c” file.</figcaption></figure>Another point of differentiation is that previously Bumblebee DLLs had two main export functions, while the new one has four.<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt3c905274f728fa88" alt="Figure 10 – “New” Bumblebee DLL Exports" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt3c905274f728fa88/6493347dd2420473b31cd636/fig10-new-bumblebee-dll-exports.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 10 – “New” Bumblebee DLL Exports</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltcb5ad0e83176edf1" alt="Figure 11 – “Old” Bumblebee DLL exports, with main “SetPath” function" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltcb5ad0e83176edf1/6493347d75c2ae82940617e7/fig11-old-bumblebee-dll-exports-with-main-setpath-function.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 11 – “Old” Bumblebee DLL exports, with main “SetPath” function</figcaption></figure>Further examination of the DLL brings us to the same main function as the previous variant.<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltec80d5d7fc0f0819" alt="Figure 12 – “SetPath” in the “new” Bumblebee DLL." src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltec80d5d7fc0f0819/6493347ee6669913502eb96f/fig12-setpath-in-the-new-bumblebee-dll.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 12 – “SetPath” in the “new” Bumblebee DLL.</figcaption></figure><h5>Conclusion</h5>Bumblebee’s latest “experiment” attempts to leverage pseudo-random sample generation as a means of reducing the risk of detection. This has been used by threat actors in the financial/banking malware landscape for years, including IcedID, which “shares” the PindOS dropper.Whether PindOS is permanently adopted by the actors behind Bumblebee and IcedID remains to be seen. If this “experiment” is successful for each of these "companion” malware operators it may become a permanent tool in their arsenal and gain popularity among other threat actors.As Bumblebee and <a href="https://thedfirreport.com/2023/05/22/icedid-macro-ends-in-nokoyawa-ransomware/" target="_blank">IcedID</a> are known to deliver ransomware, we recommend that security teams take note of these IOCs. You can find updated lists of IOCs on our <a href="https://github.com/deepinstinct/PindOS-JS-Dropper" target="_blank">GitHub page</a>.<h5>IOCs</h5><ul><li>Network Artifact User-Agent: PindOS</li><li>Bumblebee infection URLs hxxps://qaswrahc.com/wp-content/out/mn[.]php hxxp://tusaceitesesenciales.com/mn[.]php hxxp://carwashdenham.com/mn[.]php hxxps://intellectproactive.com/dist/out/mn[.]php</li><li>Bumblebee .JS dropper SHA256 bcd9b7d4ca83e96704e00e378728db06291e8e2b50d68db22efd1f8974d1ca91 07d2cb0dc0cd353fb210b065733743078e79c4a27c42872cd516a6b1fb1f00d1 00ec8f3900336c7aeb31fef4d111ee6e33f12ad451bc5119d3e50ad80b2212b0 15da5b0a65dd8135273124da0c6e52e017e3b54642f87571e82d2314aae97eec 180a935383b39501c7bdf2745b3a334841f01a7df9d063fecca587b5cc3f5e7a</li><li>Bumblebee DLL payload SHA256 24dd5c33b8a5136bdf29d0c07cf56ef0e33a285bb12696a8ff65e4065cb18359 76c9780256e195901e1c09cb8a37fb5967f9f5b36564e380e7cf2558652f875b 28c87170f2525fdecc4092fb347acd9b8350ed65e0fd584ce9fc001fd237d523 ac261ac26221505798c65c61a207f3951cc7dce2e1014409d8a765d85bfd91d4</li><li>IcedID infection URLs hxxps://masar-alulaedu.com/wp-content/woocommerce/out/berr[.]php hxxps://egyfruitcorner.com/wp-content/tareq/out/berr[.]php hxxps://tech21africa.com/wp-content/uploads/out/berr[.]php hxxps://www.posao-austrija.at/images/out/lim[.]php hxxps://logisticavirtual.org/wp-content/out/lim[.]php hxxps://adecoco.us/wp-content/out/lim[.]php hxxps://acsdxb.net/wp-content/out/lim[.]php</li><li>IcedID .JS dropper SHA256 92506fe773db7472e7782dbb5403548323e65a9eb2e4c15f9ac65ee6c4bd908b c84c84387f0b9e7bc575a008f36919448b4e6645e1f5d054e20b59be726ee814 7355656f894ae26215f979b953c8fa237dc39af857a6b27754a93adb1823f3b6 8f40ff286419eb4b0c4d15710dc552afb2c2a227a180f4b4f520d09b05724151</li><li>IcedID DLL payload SHA256 9101975f7aca998da796fc15a63b36ab8aa0fe0aed0b186aaed06a3383d5f226 4f0c9c6fc1287ef16f4683db90dd677054a1f834594494d61d765fa3f2e1352c cb307d7fa6eaac6a975ad64ff966ff6b0b0fdd59109246c2f6f5e8d50a33e93c 361b0157ef63d362fdd4399288f5f6a0e1536633dfb49c808a3590718c4d8f10 e71c9ac9ddd55b485e636840da150db5cd2791d0681123457bd40623acd8311c 8ae3be9f09f5fc64ec898a4d6467b2f6e50eaaa26fc460a4f1a9b9566e97a9a7</li></ul><h5>MITRE ATT&amp;CK</h5><table><thead><tr><th style="width: 13%;">Tactic</th><th>Technique</th><th>Description</th><th>Observable</th></tr></thead><tbody><tr><td>Execution</td><td>Command and Scripting Interpreter: JavaScript – T1059.007</td><td>Adversaries may abuse various implementations of JavaScript for execution.</td><td>.JS Droppers</td></tr><tr><td>Defense Evasion</td><td>System Binary Proxy Execution: Rundll32 – T1218.001</td><td>Adversaries may abuse rundll32.exe to proxy execution of malicious code.</td><td>Rundll32.exe usage</td></tr><tr><td>Defense Evasion</td><td>Obfuscated Files or Information – T1027</td><td>Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit.</td><td>Obfuscated JS, “Random” generated payloads</td></tr></tbody></table>

PindOS: New JavaScript Dropper Delivering Bumblebee and IcedID

blog-image-bpfdoor-malware.jpg

<h5>What is BPFdoor?</h5>BPFdoor is a Linux-specific, low-profile, passive backdoor intended to maintain a persistent, long-term foothold in already-breached networks and environments and functions primarily to ensure an attacker can re-enter an infected system over an extended period of time, post-compromise.The malware gets its name from its usage of a <a href="https://en.wikipedia.org/wiki/Berkeley_Packet_Filter" target="_blank">Berkley Packet Filter</a> – a fairly unique way of receiving its instructions and evading detection, which bypasses firewall restrictions on incoming traffic.The malware is associated with a Chinese threat actor, Red Menshen (AKA Red Dev 18), which has been observed targeting telecommunications providers across the Middle East and Asia, as well as entities in the government, education, and logistics sectors since 2021.When it was first discovered, approximately one year ago, BPFdoor was noted for its effective and elegant design and its high emphasis on stealth – an essential element in maintaining undetected long-term persistence.Recently, Deep Instinct’s threat lab observed and analyzed a previously undocumented and fully undetected new variant of BPFdoor.<h5>New, Stealthier Variant</h5>Several key differences that make this new variant even stealthier compared to the previous version include the following:<table class="text-center"><thead class="bg-grey"><tr><th style="width: 24%;">&nbsp;</th><th style="width: 38%;">“New stealthy” 2023 variant</th><th>“Old” 2022 variant</th></tr></thead><tbody><tr><td>Encryption</td><td>Static library encryption</td><td>RC4 Encryption</td></tr><tr><td>Communication</td><td>Reverse-Shell</td><td>Bind shell and iptables</td></tr><tr><td>Commands</td><td>No hardcoded commands – all commands are sent through the reverse-shell</td><td>Hardcoded commands</td></tr><tr><td>Filenames</td><td>Not hardcoded</td><td>Hardcoded</td></tr></tbody></table>One of the most significant differences compared to the previous variant lies in the removal of many of its hardcoded indicators, making the newer version more difficult to detect. Since first seen on VirusTotal in February 2023, the new variant remained undetected and is still undetected as of this writing.<h5>BPFdoor Technical Analysis</h5>When executed, the BPFdoor sample will attempt to create and get a lock on a runtime file at “/var/run/initd.lock” and will exit if it fails using that file as a makeshift mutex.<figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt6b1f7a605acf0d71" alt="Figure 1 - BPFdoor " src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt6b1f7a605acf0d71/645bce382f97ad6087afc2a7/fig01-lock-mutex.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 1 - BPFdoor "mutex" check</figcaption></figure></figure>If successful, BPFdoor will fork itself and continue to run as a child process and in this context will close its stdin, stdout, and stderr streams, and set itself to ignore the following operating system signals:<table class="text-center"><thead class="bg-grey"><tr><th style="width: 16%;">Signal Number</th><th style="width: 21%;">Signal Name</th><th>Signal Description</th></tr></thead><tbody><tr><td>1</td><td>SIGHUP</td><td>SIGHUP ("signal hang-up") is a signal sent to a process when its controlling terminal session is closed.</td></tr><tr><td>2</td><td>SIGINT</td><td>SIGINT (“signal interrupt”) is a signal sent when a user interrupts a program (Ctrl + C)</td></tr><tr><td>3</td><td>SIGQUIT</td><td>SIGQUIT is a signal sent to terminate a process.</td></tr><tr><td>13</td><td>SIGPIPE</td><td>SIGPIPE is a signal sent when a pipe breaks.</td></tr><tr><td>17</td><td>SIGCHLD</td><td>SIGCHLD is a signal sent when a child process exits.</td></tr><tr><td>21</td><td>SIGTTIN</td><td>SIGTTIN is a signal sent to a process attempting to read from the same terminal session and is blocked.</td></tr><tr><td>23</td><td>SIGTTOU</td><td>SIGTTOU is a signal sent to a process attempting to write to the same terminal session and is blocked.</td></tr></tbody></table>Ignoring these signals hardens BPFdoor against tampering with its processes.Having set up the above, BPFdoor then allocates a memory buffer and creates a socket as follows:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltb66f26dd618af2fe" alt="Figure 2 - Socket arguments" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltb66f26dd618af2fe/645bce386d595aca93fa2ebf/fig02-socket-args.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 2 - Socket arguments</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blte9215556a7459197" alt="Figure 3 - Socket creation" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blte9215556a7459197/645bce388a8445ca97101283/fig03-call-socket.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 3 - Socket creation</figcaption></figure>It will proceed to specify the following socket options using setsockopt:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltff07360ec7be9930" alt="Figure 4 - Setsockopt options" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltff07360ec7be9930/645bce388dbb82c3c233f5f4/fig04-setsockopts.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 4 - Setsockopt options</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt0e81a161934c6431" alt="Figure 5 - Call to setsockopt" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt0e81a161934c6431/645bce38e4e69e5cbc037449/fig05-call-setsockopts.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 5 - Call to setsockopt</figcaption></figure>And will read from it in a loop (further described below) using recvfrom:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt7a59c922701ee083" alt="Figure 6 - Recvfrom arguments" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt7a59c922701ee083/645bce38065c95739056107a/fig06-recvfrom.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 6 - Recvfrom arguments</figcaption></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt811bbcab6a1bb954" alt="Figure 7 - Recvfrom call" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt811bbcab6a1bb954/645bce38367cefb5428f68a2/fig07-loop-call-recvfrom.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 7 - Recvfrom call</figcaption></figure>An interesting point in the above-described flow is that the “addr” parameter is zeroed out in the call to recvfrom; it should point to a specific address from which to read data. The socket is not connected and no bind or listen calls have been made. So, what exactly is going on here?Interpreting the exact arguments that are used to create the socket reveals that the call is structured as follows:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt36f6534323294019" alt="Figure 8 - Socket call" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt36f6534323294019/645bce38367cefe17b8f689e/fig08-socket_eth.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 8 - Socket call</figcaption></figure>This creates the socket as a special packet sniffing socket which is able to read every packet that is sent to the machine from the ethernet layer and above without being bound to any specific protocol.BPFdoor employs this type of packet sniffing socket to read data with recvfrom, even without an “addr” parameter, by using the loop below to search for a specific “magic” byte sequence:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltf3c3312b0751a812" alt="Figure 9 - Looped search for " src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltf3c3312b0751a812/645bce388929af83080777c5/fig09-read-loop.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 9 - Looped search for "magic" byte sequence (highlighted)</figcaption></figure>“Magic” byte sequence: \x44\x30\xCD\x9F\x5E\x14\x27\x66Once found, the loop will break and BPFdoor will continue to Its next phase of operation.But, that creates quite a lot of traffic that BPFdoor will need to go through.Let’s examine the usage of setsockopt a bit further. When parsing its arguments, we arrive at the following code:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt734c1601420f27c9" alt="Figure 10 - Setsockopt attaches BPF" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt734c1601420f27c9/645bce4b7e7e7b9bafe70a08/fig10-setsockopt-args.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 10 - Setsockopt attaches BPF</figcaption></figure>This is where BPFdoor gets its name from. The above code that attaches a <a href="https://en.wikipedia.org/wiki/Berkeley_Packet_Filter" target="_blank">Berkley Packet Filter</a> to the socket; this is the very same mechanism that underpins infosec staples such as libpcap and allows BPFdoor to filter out “uninteresting” types of data coming through its socket.A Berkley Packet Filter can be defined as in the example below, which allows TCP over IPv4:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt89210974b140db77" alt="Figure 11 - BPF example" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt89210974b140db77/645bce4b065c95264056107e/fig11-bpf-example.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 11 - BPF example</figcaption></figure>By setting the socket option SO_ATTACH_FILTER and pointing filter to the following sock_filter_code:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt3a9b0cf5b5fbc758" alt="Figure 12 - BPF sock_filter_code" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt3a9b0cf5b5fbc758/645bce4b1f0a4c5876e36beb/fig12-sock-filter-codev3.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 12 - BPF sock_filter_code</figcaption></figure>BPFdoor guides the kernel to set up its socket to only read UDP, TCP, and SCTP traffic coming through ports 22 (ssh), 80 (http), and 443 (https).Because of its positioning at such a low level, BPFdoor does not abide by any firewall rules, and can bypass any firewall restrictions on incoming traffic and listen for packets that otherwise wouldn't have surfaced to the machine's user mode.When BPFdoor finds a packet containing its “magic” bytes in the filtered traffic it will treat it as a message from its operator and will parse out two fields and will again fork itself.The parent process will continue and monitor the filtered traffic coming through the socket while the child will treat the previously parsed fields as a Command & Control IP-Port combination and will attempt to contact it.<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt59a3decfdb9a8b40" alt="Figure 13 - Connect to Command & Control" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt59a3decfdb9a8b40/645bce4b8a84453a7a101287/fig13-connect-c2.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 13 - Connect to Command & Control</figcaption></figure>An interesting point to note, this variant of BPFdoor contains a pre-compiled version of <a href="https://github.com/libtom/libtomcrypt" target="_blank">libtomcrypt</a>, an open-source encryption library, as can be seen in the sample’s contained strings, which also offer a few additional insights:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt8e6c0a33246bf7b3" alt="Figure 14 - Contained strings" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt8e6c0a33246bf7b3/645bce4b291ca448ab7458bf/fig14-libtom-strings.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 14 - Contained strings</figcaption></figure>We can see that the library was compiled at the beginning of October 2022 using GCC on a system running Red Hat Linux. This may suggest that this variant has been operational significantly earlier than its first appearance on VirusTotal.By compiling our own version of the library in similar fashion and using bindiff to compare against BPFdoor we can see its statically linked exports:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt816a0cb45cfa1a28" alt="Figure 15 - Libtomcrypt bindiff snippet" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt816a0cb45cfa1a28/645bce4b2f97ad7a76afc2ab/fig15-libtom-bindiff.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 15 - Libtomcrypt bindiff snippet</figcaption></figure>Having made the comparison, we determined that BPFdoor is using libtomcrypt functionality to set up a secure and encrypted “reverse-shell” session with its Command & Control. This replaced its previous mechanism.After this session is established, BPFdoor will begin a loop that can be described by the following:<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="bltb2ff1c169f93cb84" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/bltb2ff1c169f93cb84/645bce3822f9986ff5c5974b/BPFDOORv2Flow.png" style="text-align: center;"/></figure><h5>Conclusion</h5>BPFdoor retains its reputation as an extremely stealthy and difficult-to-detect malware with this latest iteration.Regardless of whether one considers the encryption library compilation time (October 2022) or its initial submission to VirusTotal (February 2023) as indicative of when this sample was first put into use, it is truly amazing how long it has remained fully undetected.<figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt93ffef0dee975742" src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt93ffef0dee975742/645d25159c40aa50cb074137/fig16-vt-0detectionv3.png" style="text-align: center;"/></figure><figure style="margin-top: auto;margin-right: auto;margin-bottom: auto;margin-left: auto;text-align: center;width: auto;"><img asset_uid="blt940800074dbf8141" alt="Figure 16 & 17 - 0 VirusTotal detections, 7 different scans." src="https://images.contentstack.io/v3/assets/blt1ec077b6b53d6b3e/blt940800074dbf8141/645bce4b32acc8af715ee19b/fig17-vt-many-scans.png" style="text-align: center;"/><figcaption style="text-align: center;">Figure 16 & 17 - 0 VirusTotal detections, 7 different scans.</figcaption></figure><h5>IOCs</h5>afa8a32ec29a31f152ba20a30eb483520fe50f2dce6c9aa9135d88f7c9c511d7 – BPFDoor ELF SHA256 /var/run/initd.lock – BPFDoor "mutex”<h5>MITRE ATT&CK:</h5><table class="text-center"><thead class="bg-grey"><tr><th style="width: 20%;">Tactic</th><th>Technique</th><th>Description</th><th style="width: 20%;">Observable</th></tr></thead><tbody><tr><td>Command and Control Defense Evasion Persistence</td><td>T1205 - Traffic Signaling</td><td>Attacker employs “magic” values to trigger response.</td><td>“Magic” byte sequence</td></tr><tr><td>Command and Control Defense Evasion Persistence</td><td>T1205.002 - Traffic Signaling: Socket Filters</td><td>Attacker attaches filter to a network socket.</td><td>Usage of Berkley Packet Filter</td></tr><tr><td>Command and Control</td><td>T1573 - Encrypted Channel</td><td>Attacker employs encrypted Command & Control communication.</td><td>Usage of libtomcrypt</td></tr><tr><td>Execution</td><td>T1106 – Native API</td><td>Attacker calls upon native OS APIs in order to execute behaviors.</td><td>Usage of popen</td></tr></tbody></table>Earlier variant analysis: <a href="https://www.elastic.co/security-labs/a-peek-behind-the-bpfdoor" target="_blank">https://www.elastic.co/security-labs/a-peek-behind-the-bpfdoor</a>Deep Instinct takes a prevention-first approach to stopping ransomware and other malware using the world’s first and only purpose-built, deep learning cybersecurity framework. We prevent ransomware, zero-day threats, and previously unknown malware in &lt;20 milliseconds, 750x faster than the fastest ransomware can encrypt. Deep Instinct has &gt;99% zero-day accuracy and promises a &lt;0.1% false positive rate. The Deep Instinct Prevention Platform is an essential addition to every security stack – providing complete, multi-layered protection against threats across hybrid environments.

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