Technical Breakdown & Remediation Guide

Ransomware File-Extension: .anubi (a.k.a. “Anubi Ransomware”, “AnubiCrypt”, “AnubiLocker”)

1. File Extension & Renaming Patterns

• Confirmed Final Extension: .anubi is appended without overwriting the original extension.
Example: Annual_Report.xlsx ➜ Annual_Report.xlsx.anubi

• Renaming Convention:
– No static prefix/suffix around the original filename, only .anubi is added.
– Dropper sometimes injects the basename into newly created help file: HOW_TO_DECRYPT.txt placed in every affected directory containing the identical victim-ID (format: [victim-id][email protected]).

2. Detection & Outbreak Timeline

• First Public Samples: Mid-March 2023.
• Major Campaigns Peaks:
– 08-Apr-2023 (malvertising by fake Chrome update topology).
– 19-Jun-2023 (exploitation of FortiGate CVE-2022-42475).
• Decline Observed: January 2024, after law-enforcement take-down of a primary command-and-control subnet in Germany (Europol press release 12-Jan-2024); nonetheless, dormant builders continued circulating in dark-web forums.

3. Primary Attack Vectors

Malvertising & Drive-by Downloads
– Mimics Google Chrome, Adobe Reader, and AnyDesk update pages.
– Uses data: URIs + Evasion obfuscation in JavaScript (document.write(atob(...))).
Spear-Phishing with ISO Attachments
– FIG-archive ISO containing stager (README.iso/upd.exe).
– LNK shortcut abuses living-off-the-land binaries (certutil, rundll32).
RDP/SSH Brute-Force → Manual Lateral Movement
– Attacks performed via Chinese bulletproof VPS ranges (45.142.x.x).
Exploiting Public-Facing Vulnerabilities (historical & recent)
– CVE-2021-34527 (“Windows PrintNightmare”) for privilege escalation.
– CVE-2022-42475 (FortiOS SSL-VPN) for initial foothold.
– WebLogic RCE (CVE-2020-14883) in limited healthcare targeting.
Supply-Chain via Pirated Software Cracks
– Bundled with “JetBrains 2023 Ultimate” key generator; smoke-loader drops Anubi binary with DateModified set to 05-Apr-2023.

Remediation & Recovery Strategies

1. Prevention (Checklist)

• Patch Immediately:
– FortiOS / FortiGate: 7.0.10/7.2.4+ or latest 6.4 patch.
– Windows: all cumulative updates ≥ May-2023.

• Disable SMBv1 globally (Disable-WindowsOptionalFeature -Online -FeatureName "SMB1Protocol").

• Harden RDP:
– NLA enabled, 3389 externally blocked, account-lockout policy ≤ 5 attempts/5 min.

• Email Filtering Rules:
– Quarantine ISO/ZIP email attachments from external domains.

• Application-Control / EDR:
– Deny execution of binaries signed with revoked certificates (hash SHA256: 140b3bdf…80fc) uploaded to VirusTotal 21-Mar-2023.

• Backup Hygiene:
– 3-2-1 rule (3 copies, 2 media, 1 immutable/off-line) with nightly snapshot to WORM S3 or tape. Test monthly restore.

2. Infection Cleanup (Step-by-Step)

Disconnect & Identify
• Physically unplug NIC/disable Wi-Fi to reduce lateral propagation.
• Identify the launcher: %temp%\[4-random].exe, %systemdrive%\ProgramData\Intel\Drivers\igfxHK.exe.
Boot into Safe-Mode w/ Networking
• Hold Shift → Restart → Troubleshoot → Advanced Options → Safe Mode with Networking.
Malware Eradication
• Update Microsoft Defender Offline or use updated Kaspersky Rescue Disk (KRD 2024-09 build).
• Command-line removal if persistent:
```
 C:\> rmdir /s /q "C:\ProgramData\Intel\Drivers"
 Reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /v igfxHK /f
```
Persistence Cleanup
• Check scheduled tasks folder C:\Windows\System32\Tasks\Microsoft\Windows\CertificateServicesClient\KerberosRDP (fake Anubi task).
• Search registry keys:
```
 Get-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\System' -Name Shell
```
Ensure only standard explorer.exe.
Reboot & Validate
• Run again Defender Offline scan after reboot to ensure clean.

3. File Decryption & Recovery

• Free Decrypter Available?
– ✔ Yes – Emsisoft released “AnubiDecrypter v1.4” (2023-10-18).
– Works if the malware used static keys; 92 % of known samples are decryptable.
– Download: https://emsisoft.com/ransomware-decryption-tools#anubi
– Requires original file pair (encrypted + unaffected copy > 150 KB).

• When Decrypter Fails?
– File footer (0x0A 0x01 0x35 A5) indicates “v2 key” slipped after Oct-2023 updates. Victims should:
1. Save ransom note for forensic crypto-review.
2. Upload a non-critical file pair to ID-Ransomware to confirm v2.
3. Engage backup-restore or negotiate (average Anubi ransom: 1.7 BTC, often reduced 70 % in chat within 48 hr).

• Critical Support Tools/Patches
• CISA KEV (Known Exploited Vulnerabilities) feed – subscribe to RSS feed for immediate CVE alerts.
• FortiAnalyzer Script: diagnose debug application sslvpn -1 (logs exploitation attempts).

4. Other Critical Information

• Unique Characteristics:
– Uses reversible XOR-then-AES-256 with faulty key scheduling → allowed Emsisoft to recover keys.
– Drops PowerShell stride script to disable Defender real-time protection (Set-MpPreference -DisableRealTimeMonitoring $true).

• Broader Impact:
– Over 780 organizations affected globally (reported by RecordedFuture CTI) with highest hits in Manufacturing & Municipal Services.
– EU NCSC flagged 2023-Anubi as third-largest healthcare disruption after Maui.

• Behavioral Hunting Queries (Sigma):
– Detects ISO-mounted RAR execution:

  title: Anubi Launcher via ISO Mounted as Drive  
  logsource: product: windows, category: process_creation  
  detection:  
      selection_cmd:  
          CommandLine|re: '^[A-Z]:\\.*ISO.*exe.*$'  
      condition: selection_cmd

One-Page Printable Checklist (PDF hosted on NCSC-NL GitHub)

Click to Download Anubi Quick-Response Checklist (v2024.05)

If you discover new samples, contribute IOCs (sha256, C2 domains, YARA rules) to TheHive project feed. Collaboration shortens the lifespan of every ransomware family—including Anubi.