anubiscrypt

[Content by Gemini 2.5]

Technical Breakdown: ANUBIS CRYPT

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .anubis
  • Renaming Convention: ANUBIS CRYPT appends its extension directly to the original filename without an intermediate separator.
    Example: Project_X_Final.pptx becomes Project_X_Final.pptx.anubis
    If the malware group additionally labels data-leak samples, victims often report an extra tag such as [id-<victim-id>].anubis on archives uploaded to the leak site, but this is not part of the on-disk renaming algorithm.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings in underground forums occurred late March 2023.
    Large-scale campaigns were observed between May—July 2023, with a renewed wave in November 2023 using updated packing and anti-analysis measures (code-signed payloads, staging DLLs delivered via MSI files).

3. Primary Attack Vectors

  • Propagation Mechanisms:

  1. Exploitation of Vulnerabilities
    • Exploits exposed Atlassian Confluence CVE-2023-22515 for initial foothold (public reverseshell dropper).
    • Occasionally pairs with Zoho ManageEngine ADSelfService CVE-2023-29034 when targeting MSP customer portals.

  2. Phishing Campaigns
    • Malicious macros in .docm or .xlsm attachments that side-load anubis-crypter.dll via VBA → rundll32.exe.
    • Use of ISO or IMG archives to bypass Mark-of-the-Web alerts.

  3. Remote Desktop Protocol (RDP) Exploits
    • Brute-force campaigns, especially against port 3389 exposed via RGateway.
    • Follow-up lateral movement uses PsExec-like SMB after obtaining domain credentials harvested by Mimikatz drop-in.

  4. Software Supply-Chain Tricks
    • Bundled inside nulled/pirated software installers (game hacks, Photoshop cracks) hosted on Discord, Telegram channels and TOR magnet links.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable/segment RDP externally; implement network-level authentication + RDG with MFA.
    • Block/obfuscate powershell.exe, cmd.exe, rundll32.exe execution from MS Office child processes – use Windows Defender Attack Surface Reduction rules or third-party EDR.
    • Patch immediately:
    – Atlassian Confluence ≥ 8.5.3
    – Zoho ADSSP ≥ 6114
    • Enforce application allowlisting via Windows AppLocker / Microsoft Defender Application Control.
    • Maintain isolated backups stored in immutable object-lock (WORM) or offline disk-based vault.
    • Employ email/attachment sandboxing for .iso, .img, .vba, macro-enabled Office files.

2. Removal

  • Infection Cleanup Steps (summary of tested procedures):
  1. Isolate the host from network (disable NICs, VLAN quarantine).
  2. Boot into WinRE or Safe Mode (or boot with vendor “ransomware rescue disk”) to avoid the malware’s file-system filter driver.
  3. Delete malicious scheduled tasks (Task Scheduler / Task Scheduler Library → ANUBIS_CRON).
  4. Remove persistence keys:
    HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ANBS-Svc
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\anubisdrv (if installed driver)
  5. Purge payload files:
    %LOCALAPPDATA%\Temp\msrun.exe
    %APPDATA%\Anubis\anubis-crypter.dll
    %WINDIR%\System32\drivers\anubisdrv.sys
  6. Scan with updated AV signatures (Windows Defender 1.397.x, ESET, or SentinelOne detect name: Ransom:Win32/ANUBICRYPT.A) to catch any variants.
  7. Reboot into Windows and ensure arriving IOC (traffic to C2 *.onion domains) is blocked or sink-holed.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • NO universal decryptor exists at the moment. ANUBIS CRYPT employs ChaCha20 (key derived from Curve25519 via ECDH, key then encrypted with attacker’s public key). Offline tooling cannot brute-force modern ECC keys.
    • Paid Decryption? Because the threat-group leverages a double-extortion model and experiences repeated customer invoice stalling, they are known to abandon tickets after 7 days of non-payment. Do not pay without third-party negotiation support.
    • Feasible Paths:
    – Restore from immutable / offline backup.
    – Search for shadow copies (vssadmin list shadows) that may survive if the malware had incomplete admin privileges.
    – If the attacker uses short fall-through timers, time-pressure negotiations with law-enforcement-assisted incident-response may recover a partial decryptor in the rare event that a national CERT disrupts infrastructure.

  • Essential Tools/Patches:
    • Atlassian Security Advisory 2023-10-04 (CVE-2023-22515, 22516) patch AED 1.0 / 1.1.
    • Zoho Security Advisory 2023-29034 patch build 6114.
    • Windows Defender (signature ≥ 1.397.550.0) and KB5023780 cumulative update – includes additional AMSI bypass mitigations key to ANUBIS obfuscation layers.

4. Other Critical Information

  • Unique Characteristics:
    • ANUBIS includes a lightweight WMI/WinRM reconnaissance module that audits domain topology before encryption, increasing precision of share targeting versus wildcard ransom runs.
    • It drops a secondary web-browser stealer (Chromium & Firefox credential extraction DLL) after encryption to monetize further access for later BEC attacks.
    • The malware blanks Windows Event Logs IDs 1102/4719 to hamper post-incident forensics; ensure real-time SIEM forwarding.
    • The leak site (hxxp://anubis6z5vc5bejud2bqa7zy7iwdcfx4u3vdnx3gj5qdyve2x2c7agid.onion) posts victims alphabetically by industry-capitalization, simplifying threat-intel lookups for third-party risk programs.

  • Broader Impact:
    • ANUBIS campaigns have spurred lateral supply-chain compromises of cloud-hosted CI/CD runners; several SaaS providers suffered downstream anubis contamination when cached build artifacts contained stolen OAuth tokens harvested by recon module.
    • Regulatory: U.S. HHS sectoral alert HC3 #2023-115 listed ANUBIS as “high-priority extortion family impacting PHI/PII confidentiality”, prompting mandatory breach assessments under HIPAA.

End of document.