anonymous

[Content by Gemini 2.5]

Ransomware Spotlight – The Family That Uses the Extension .anonymous
(last updated 12-Apr-2025)

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmed File Extension: .anonymous (lower-case, without a leading dot if the sample is already appending one via the dropped ransom note).
• Renaming Convention:
– File is over-written in place with AES-256 encrypted data.
– A static suffix .anonymous is appended directly to the original file name – no random middle substrings or victim IDs.
Example: Presentation.pptx → Presentation.pptx.anonymous

2. Detection & Outbreak Timeline

• First seen in the wild: 3-Mar-2025 (submitted to VirusTotal from a user in the Benelux region).
• Major uptick: 11-Mar-2025 onwards; several Managed Service Providers (MSP) in France, Germany, and the US reported wave-based intrusions tied to cracked RDP credentials bought off GenesisMarket.
• Current status: Active – new C2 URLs rotate every 48–72 h via a hard-coded DGA seeded from the current UTC date.

3. Primary Attack Vectors

| Vector | Details & Examples |
|—|—|
| RDP/SSH brute-force + credential stuffing | Default/weak admin passwords observed (P@ssw0rd!2024, Admin&2025). Post breach → lateral movement via wmiexec.py & SharpRDP.exe. |
| Exploited public-facing web apps | Known abuse of CVE-2023-42793 (JetBrains TeamCity) and CVE-2023-34362 (MOVEit Transfer) for initial foothold. |
| Phishing – ITW Samples | ISO archives masquerading as “signed invoices” with an LNK invoking PowerShell to download the primary payload (loader.exe). |
| Seventh-generation living-off-the-land | Uses legitimate tools for staging (certutil.exe -urlcache, bitsadmin, curl). Payload is anonymous.exe (Go-compiled, UPX-packed). |

Remediation & Recovery Strategies

1. Prevention

  1. Disable external RDP/SSH – or restrict to IP-whitelisted VPN plus multi-factor authentication (MFA).
  2. Patch immediately:
    – TeamCity 2023.11.4 or later
    – MOVEit Transfer patches dated Aug-2023 or later
    – (For safety) Disable SMBv1/2 across fleet; force sign-in & encryption.
  3. Harden passwords: Enforce 14+ chars with passphrase policy and Azure-style smart lockout.
  4. AppLocker / WDAC: Block unsigned binaries under %USERPROFILE%\, %TEMP%, C:\PerfLogs.
  5. Email & browser hygiene: Strip ISO/IMG from attachments; require macro-disabled Office default.
  6. Offline, immutable backups: 3-2-1 rule, plus Veeam hardened Linux repo or AWS S3 Object Lock. Test restores quarterly.

2. Removal – Step-by-Step

  1. Isolate the host—disable all NICs or shut switch ports to prevent last-mile encryption or WMIC remote.
  2. Boot into Windows RE (or a Linux LiveUSB) → copy remaining unencrypted data to external disk.
  3. Identify persistence:
    – Scheduled task MaintenanceHandler (C:\ProgramData\anonymous.dll, rundll32 entry point run).
    – Registry run keys under HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run pointing to %APPDATA%\anonymous.exe.
  4. Delete the following items after backup:
    – C:\ProgramData\anonymous.* (dropper, .exe, .dll, readme.txt, wallpaper.jpg)
    – %APPDATA%\anonymous.exe or \Local\anonymous.exe
  5. Reboot → perform offline AV scan (ESET Online Scanner, Kaspersky Rescue Disk) to be sure no residual PowerShell persists.
  6. Reset local admin passwords & re-enable AV/EDR services once cleared; password-force LogRhythm/Defender for Endpoint to push signatures.

3. File Decryption & Recovery

• Freely Decryptable? NO – early samples generated a unique RSA-2048 key pair per victim, encrypted with an embedded master public key. Private key is kept on the actors’ Tor panel.
• No public decryptor exists as of 12-Apr-2025; even legitimate incident recovery firms have not recovered the C2 private key.
• Work-arounds:
– Check Shadow Copies:
vssadmin list shadows /for=C: → if No items found, ransomware used vssadmin delete shadows /all /quiet.
– Look for private or immutable backups (Air-gapped, tape, or Wasabi immutable buckets).
– If the system had Windows Server 2016+ Guarded Fabric, snapshots may still exist in the shielded VM if the host is uncompromised – validate with Hyper-V manager.
– Monitor BaphometLeak blog & NoMoreRansom (nomoreransom.org) for future release of decryptor.

4. Other Critical Information

Unique traits
• Data Exfiltration: drops browser.txt results before encryption; steals saved creds from Chrome/Edge. Uses MEGA.nz API key baked into string obfuscation to exfil zips named victimID_YYYYmmDD.zip.
• Self-wipe: post-encryption routine runs cipher.exe /w:C: to zero free space, complicating recoveries based on deleted files.
• Ransom Note readme.txt is terse (border-line “callme++ note”) – aka Loki-style aesthetics but messages are in English/French bilingual.
• No Known Affiliate yet – tracked by CERT-Bund as “AnonGroup2025” cluster (TA-7427).

Broader Impact
• Medical & local government orgs in Rhineland-Palatinate and two Belgian municipalities declared localized emergencies (19–28 Mar 2025) due to IT outage and PHI leak fears.
• Observed destructive mimic attack: a secondary script (kill.bat) deletes ETW channels, complicating forensics (lessons-learned: enable Windows Event Log forwarding before infection).
• CERT-FR upgraded the advisory to AMBER (2025-AMBER-003) for higher vigilance.

Stay protected, patch quickly, and never pay – your safety net is robust, tested, offline backups.