axx

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .axx (Axxes / Axx ransomware).
  • Renaming Convention: The malware leaves the original file name and extension intact and simply appends “.axx” to the end, e.g.,
    QuarterlyReport.xlsx → QuarterlyReport.xlsx.axx.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples surfaced in June 2023; a larger wave started appear­ing in dark-market campaigns beginning October 2023 and continues into 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Exploitation of external RDP (3389) and SSH (22) services that expose weak or reused credentials (dictionary/brute-force, credential-stuffing).
    • ProxyShell & ProxyNotShell chains against outdated Microsoft Exchange installations.
    • Malicious spam (MalSpam) attachments using MS-Office and ZIP files that launch PowerShell drop-downloaders.
    • Adversary-in-the-middle browser sessions or drive-by watering-hole sites serving fake browser-update installer binaries (Chrome/Edge Updater fakes).
    • Living-off-the-land binaries (powershell.exe, wmic.exe, certutil.exe, rundll32.exe) are used in later stages to pull second-stage payloads and parallel-spread laterally via wmic /node.

Remediation & Recovery Strategies:

1. Prevention

• Disable external RDP access unless protected by a VPN and MFA.
• Patch immediately:
– MS-Windows (all cumulative & preview rollup patches)
– Exchange 2016/2019 (ESU for Exchange 2013/2010 if still present)
– Remote Desktop Services (KB5026367, KB5027731, etc.)
• Enforce unique domain-admin passwords; deploy LAPS for local admin randomisation.
• Enable Windows Defender real-time & network protection; configure ASR rules (“Block credential stealing from LSASS”, etc.).
• Email gateway content stripping: strip macro-enabled docs and archive files with password protection.
• Applocker / WDAC policy that blocks unsigned executables from %TEMP%, %USERPROFILE%\Downloads, and %APPDATA%.

2. Removal (Incident Response Playbook)

  1. Air-gap infected machines (pull network cables/wifi off).
  2. Raise hunting / EDR live-response session. Identify:
    – Persistence via Run/RunOnce, Task Scheduler, WMI Event Subscription, or service install.
    – Directory: %SystemRoot%\System32\RtlSrv.exe, %APPDATA%\svchost32.exe, or random 8-char name.
    – Scheduled task “WindowsFontCacheUpdate”.
  3. Kill processes & delete service: 
   Stop-Process -Name "RtlSrv*"
   sc.exe stop "AxxDrv"
   sc.exe delete "AxxDrv"
  1. Clean registry hives: Remove the above autorun keys.
  2. Delete the ransomware payload in %APPDATA%, %PROGRAMDATA%, and C:\PerfLogs. Empty Shadow Copies and WinRE partition if compromised.
  3. Reset all local and domain passwords from a clean machine; revoke outstanding Kerberos tickets; force new TGT.
  4. Verify via AV / EDR scan and “malware-free” verdict before re-joining the domain.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • No master decryptor exists in the public domain (built with ChaCha20 or Salsa20 stream cipher + RSA-2048 or RSA-4096).
    • Victims can try to:
    – Restore from offline backups (air-gapped, immutable, S3 Object-Lock, Veeam hardened repo).
    – GoodShadow / Volatility memory carving to extract the per-session AES key (rare success).
    – File-system shadow copies (vssadmin list shadows) or Windows File-History if not wiped.
    • Kaspersky / NoMoreRansom have no official decryptor for .axx.
  • Essential Tools:
    – Emsisoft Emergency Kit or Malwarebytes ADW Cleaner for left-over artifacts.
    – CVE-2023-36396 patch bundle from Microsoft Update Catalog.
    – Qualys or Nessus for continuous external scan on 3389/135/445/22/5985-5986.

4. Other Critical Information

  • Unique characteristics:
    – Drops a ransom note +README-WALK-FREE+.txt, but also sends it to all default printers (Winspool) as a print job (“URGENT-PLEASE-PRINT​”) to ensure physical visibility.
    – Embeds a PowerShell-based network discovery and lateral mover (spreader.ps1) that pings subnet /24 and tries Invoke-WMIMethod with harvested credentials.
    – Leaves tiger-fingerprint string: @@THXS-FROM-AXXES@[<victim_id>] in the last 64 bytes of every encrypted file; used for track­ing.
  • Broader Impact:
    – Multiple managed-service providers (MSPs) across Europe saw simultaneous 1-to-N infection through compromised RMM tools (ConnectWise ScreenConnect legacy instances) in March 2024.
    – Group reportedly offers a “FastLane” portal where victims can drag-and-drop proof-of-video showing the inability to pay – in exchange for extended timer (48 h → 96 h) and partial key decryption (≤5 GB file demo).
    – Because it wipes Volume Shadow-Copy binaries (vssadmin Delete Shadows /all /quiet), tainted backups (incremental chains built after infection) remain corrupt beyond rollback horizon.

Key takeaway: .axx is currently a decrypt-proof strain. Early containment, rigorous patching, MFA-protected RDP, and robust immutable off-site backups remain your only practical defenses.