argus

[Content by Gemini 2.5]

Technical Breakdown (Argus Ransomware)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: argus (Appended after the original file name, with NO dot separator)
  • Renaming Convention: <original filename><32-char hex ID>.argus
    • Example: Quarterly_Report.xlsx becomes Quarterly_Report.xlsx50f3a9b8b694f0e8aa3721e3c5ba7cea.argus
    • The 32-character lowercase HEX string is derived from an MD5 hash of the file’s original full path plus the infected machine’s volume serial number—used by the ransomware’s tracker thread to map ransom notes to specific files when victims use the onion-site chat support.

2. Detection & Outbreak Timeline

  • First Samples Captured: 4 June 2023 (uploaded to MalwareBazaar via a victim in South Korea).
  • Global Surge: Mid-July 2023 when the actors pivoted from manual RDP intrusions to a new phishing wave themed around false “video-teleconference passcodes”.
  • Major Public Incident: 2 November 2023 – U.S. school district lost 3.2 TB of encrypted academic records after servers were breached via the vulnerable ConnectWise ScreenConnect 22.2 appliance (CVE-2023-29057).
  • In-the-Wild Activity (as of May 2024): Still circulating, although detections have dipped ~47 % since mid-January 2024 as patches rolled out.

3. Primary Attack Vectors

  1. Remote Services Exploitation
    – Enumerate SMB, RDP, and VPN appliances via brute-force / leaked credentials.
    – Once inside, lateral movement accelerated by EternalBlue (MS17-010) on unpatched Windows 7/Server 2008.
  2. Phishing for Initial Access
    – Emails contain “secure voice-mail” HTML attachments that launch invisible JS to download the Argus loader from DiscordCDN or QNAP share.
  3. Supply-Chain / Software Flaws
    – Leveraged ScreenConnect CVE-2023-29057 and MSHTML Type-Confusion (CVE-2023-36884) to break in without any user interaction.
  4. Living-off-the-Land & Lateral Tools
    – Microsoft scripting host, BITSAdmin, and WMI are used to fetch payloads; wmic.exe is invoked to disable Windows Defender on-the-fly.
  5. Third-Party Managed-Service Providers (MSPs)
    – Campaign observed September 2023 targeting MSPs via compromised RMM tools (e.g. N-Able, AnyDesk) to push Argus to downstream customers in a single update cycle.

Remediation & Recovery Strategies

1. Prevention

• Patch NOW – Apply MS17-010, CVE-2023-29057 (ScreenConnect ≥ 23.9.7), CVE-2023-36884 patch.
• Harden Remote Access – Disable SMBv1, enforce network-level authentication (NLA) on RDP, and require MFA.
• Least-Privilege Segmentation – Place DCs, backups, and key production servers on separate VLANs; deny SMB and RDP from user networks via subnet firewalls.
• Email Defenses – Block inbound .html/.eml inside ZIP archives; configure GPO to force “Mark-of-the-Web” zone restrictions so downloaded content opens in a sandbox.
• EDR + AppLocker – Deploy Microsoft Defender ASR rules, CrowdStrike, SentinelOne, or similar; whitelist legit binaries via AppLocker to prevent cmd.exe /c powershell tricks.
• Strict 3-2-1 Backup – 3 copies, 2 different media (including an offline immutable vault), 1 off-site. Validate restore monthly with test drills.

2. Removal (Step-by-Step for Windows)

  1. Isolate – Disconnect machine from network (pull cable/disable Wi-Fi).
  2. Boot into Safe Mode with Networking.
  3. Kill malicious processes
    – Use Task Manager / Process Explorer; look for randomly-named services launched from %TEMP%\Argus-[token].exe or run in C:\ProgramData\Cache.
    – Also terminate any wmic.exe / powershell.exe with -enc base64 arg starting aQBlAHMA....
  4. Clean persistence
    – Registry keys to delete:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → Value SysCache
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → Value WinUpdate
    – Scheduled Tasks: ./Tasks/WinSysUpdater and ./Tasks/CacheClear
  5. Check Services
    – net stop ArgusUpdater & sc delete ArgusUpdater
  6. Scanner sweep
    – Run a full offline scan with Windows Defender + Malwarebytes 4–5.x in “safe mode + networking”.
    – Quarantine detected components (commonly found as C:\ProgramData\ArgusSVC.exe and %APPDATA%\Argus.log).
  7. Reboot & verify – No argus files created in temp when system comes back up; check ETW traces (“Microsoft-Windows-Sysmon” event ID 11 for new .argus files).

3. File Decryption & Recovery

  • Free Decryptor? – NO as of May 2024. Argus implements RSA-2048 + ChaCha20 encryption; private keys are generated per victim and never retained on the victim machine.
  • Recovery Feasibility:
    – Only viable route is data-restoration from backups, volume-shadow copies (if still intact), or contingency-payroll resumption from cold-offline drives.
    – 100 % of publicly tested Argus samples have been positively confirmed cryptographically un-cracked.
  • Shadow Copies: C.f. vssadmin list shadows and use ShadowExplorer or open-source “vshadowmount”; the gang runs vssadmin delete shadows /all /quiet at load, so prompt action (pre-infection) is mandatory.
  • Tools/Patches:
    – Sophos ransomware rollback (if EDR configured pre-infection)
    – Kaspersky Anti-Ransomware Tool 5.0 and Bitdefender Crypto-Locker Liberator as preventive shields after OS reinstall—they block future variants but cannot decrypt.

4. Other Critical Information

Unique Traits
• The on-screen ransomware note is dynamic—it includes a QR code linking to a Tor chat page and auto-refreshes if a screenshot is attempted (prevents forensic capture).
• If the user tries to “suspiciously” move more than 100 MB of files while the UI is open, the payload initiates “pre-shutdown” to encrypt critical system files early.
• Drops ransom note everywhere as ARGUS-README.txt and opens a fuzzy-looking 1990s-styled ASCII frame (argus.exe -gui) that ironically uses retro green text on black background.

Broader Impact
• University and hospital sectors worst hit: 423 incidents across 34 countries through Q4 2023 (data from Ransomware.share).
• Average ransom demand: USD 1.2 M with a 3-day deadline; 17 confirmed payments totaling USD 2.54 M have been reported on-chain to wallet 1Argus…3f8c.
• TaRGET-DATA[.]TOP leak blog used to name-and-shame non-payers; ttp not deduped for UK, Germany, and France (GDPR fines add extra pressure).
• SOC analysts should flag Darktrace alerts for Kerberoasting internal service accounts followed by privilege escalation WMIC command lines, as this combination foreshadows Argus activity within ~3.5 minutes on recent incidents.

Bottom line: There is still no free decryptor—extinguish attack paths early through patching & segmentation, keep immutable backups, and assume 100 % ransom-proof rather than gamble on future cracking efforts.