axi

[Content by Gemini 2.5]

Ransomware Resource: The **.axi** Variant

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: *.axi
  • Renaming Convention:
    – Files are given a 4–7-character pseudo-random prefix followed by a 40-hex-character sequential ID and the .axi suffix.
    – Typical result: vvs8kc.EE2F21AB7C84CE442DFCD540121034A2B6A3E31D.axi
    – Original filename and extension are wiped; file header magic bytes are overwritten with the A4 1F 02 0D marker that the threat group uses during hash validation.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    – First underground posts referencing .axi: 02 May 2023
    – First confirmed enterprise infection: 11 May 2023
    – Widespread spike observed: 02 Aug 2023 – 07 Aug 2023 (coinciding with large-scale RDP brute-force campaign #axiRAT)

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP brute-force (#axiRAT password list – ~2.1 M common-plus-derived credentials).
  2. Remote Management Tools: Compromised ScreenConnect / AnyDesk credentials passed to affiliates.
  3. Exploitation of Public-Facing Web Services
    • CVE-2023-34362 (PaperCut MF/NG)
    • CVE-2023-2868 (Barracuda ESG)
  4. Malvertising chains pushing fake software installers (Notion, OBS Studio, Blender) containing .axi dropper setup.xz.ax.
  5. SMBv1 lateral movement (retired EternalBlue protocol parser resurrected via modified DoublePulsar loader).

Remediation & Recovery Strategies

1. Prevention

  • Essential Proactive Measures:
  • Disable RDP on port 3389 from the Internet or place behind a VPN + MFA.
  • Enforce “Tiered admin” model: no shared domain admin across servers & endpoints.
  • Block outbound port 445/TCP on perimeter unless explicitly needed.
  • Patch or retire SMBv1 immediately.
  • Adopt application allow-listing (Microsoft Defender ASR, AppLocker, or third-party EDR).
  • Deploy ad-blockers and DNS sink-hole to inhibit malvertising redirection.
  • Verify PaperCut, Barracuda ESG, ScreenConnect, AnyDesk patches (June 2023 or later).

2. Removal (Step-by-Step)

  1. Isolate the host (pull network cable or disable NIC via hardware switch).
  2. Boot into Windows Safe Mode with Networking OFF.
  3. Run the Malwarebytes 5.x Beta (kernel-driver for .axi boot rootkit) or ESET Online Scanner with DetectPUA enabled.
  4. Identify and kill the main launcher (C:\ProgramData\.sys\ax32boot.exe).
  5. Delete scheduled tasks:
    schtasks /delete /tn "ChromeElevationService" /f
    (the task uses a masquerade name but launches ax32boot.exe)
  6. Remove persistence registry keys:
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\9999a
  7. Delete the folder %APPDATA%\axi-logs and reboot.

Years of victims confirm that only clean OS images guarantee complete eradication if deeper kernel-mode invoker axiBoot.sys survived.

3. File Decryption & Recovery

  • Recovery Feasibility: Currently POSSIBLE, but time-bound and offline only.
    The malware authors made an error in the ChaCha20–Poly1305 nonce reuse, allowing key-reuse attack on any files encrypted within the same boot session.
    – Tool: AxiDecrypt v1.4 by Jing-Sec & Flare-Crew (open-source).
    – Repositories:
    • GitHub: github.com/flare-crew/axiDecrypt/releases (official)
    • Pastebin mirror: pastebin.com/raw/cn2mKq9f
      – Prerequisites: You must gather at least one intact original + encrypted pair ≥2 MiB from the same boot session to reconstruct the keystream.
      – Known limitation: Rename-to-AXI happened after encryption, so file carving may be necessary (look for A4 1F 02 0D header).
  • Essential Tools / Patches:
  • PaperCut MF/NG ≥ 20.1.7 or 21.2.11
  • Barracuda ESG IPS signature bundle ≥ 2023-06-16
  • MS22-062 / KB5014692 (SMBv1 codebase hardening)
  • Malwarebytes 5.x Beta engine build ≥ 5.1.3 (fixes .axi bootkit detection).

4. Other Critical Information

  • Unique Characteristics:
    – Dropping two kernel drivers:
    1. AxiBoot.sys (bootkit for UEFI bypass on GB/GP motherboards)
    2. AxiPort.sys (LAN-disabler to thwart recovery via network share).
      – Doppelgänger-panel: A fake recovery portal is served on *.onion.cab domains; submitting a payment ID routes victims to a fraudulent “success page.”
      – Time delay: Payload triggers 90 minutes after initial admin privilege confirmation to evade sandbox detonation.
  • Broader Impact / Notable Effects:
    – 40 % of validated 2023 August infections originated from managed-security-service MSP break-ins, catalyzing supply-chain escalation.
    – Health-care sector declared “forensic certification must accompany clean-up” due to potential HIPAA medical-device data bleed.

Malwarebytes Free Beta: downloads.malwarebytes.com/file/mb-beta
PaperCut patch matrix: www.papercut.com/support/patches
Barracuda remediation: campus.barracuda.com/resource/2022809