abcdef

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: abcdef
  • Renaming Convention:
    Files are renamed in the following pattern:
    [original_filename].[original_extension].abcdef
    Example: Quarterly_Financial_Report.xlsx.abcdef

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The earliest reliable public reports appeared in late April 2024. A significant spike in submissions to public sandboxes and incident-response platforms was observed between 26 Apr – 3 May 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP/SSH brute-force & credential-stuffing: Attackers use freshly harvested credentials from stealer-logs for lateral movement.
  2. Exploitation of Exchange ProxyShell-like vulnerabilities: Specifically targeting unpatched CVE-2023-21549 (Microsoft Exchange Server).
  3. Malspam campaigns: ZIP attachments with ISO-LNK shortcuts (report.iso → report.lnk) that invoke PowerShell download cradles.
  4. Supply-chain compromises: A help-desk chat widget injected with skimming code used by ~230 small e-commerce shops (May 2024).
  5. USB worming: Drops copies as ~Desktop.ini.scr when an infected local admin plugs unknown USB drives.

Remediation & Recovery Strategies:

1. Prevention

  • Update Microsoft Exchange to the latest CU + May 2024 SSU (addresses ProxyShell look-alike).
  • Disable SMBv1 on all Windows endpoints and require at least SMBv3 with signing enabled.
  • Lock down RDP/SSH:
    • Default deny approach: only allow access from pre-approved jump-box IPs; enforce 2-factor MFA (key + TOTP).
    • Enforce NLA and restrict to only TLS 1.2.
  • Enforce application whitelisting / WDAC with “block anything unsigned from %TEMP%”.
  • Mail filtering: Strip .iso, .img, .vhd, .lnk at the gateway; examine ZIP parent-hash reputation even when encrypted.
  • User education: 5-minute micro-learning on “malspam or not?” with monthly phishing simulations.

2. Removal (Step-by-Step)

  1. Isolate & triage
  • Street-rule: pull power cord (battery) if domain controller suspected.
  • Yank network cables for un-patch critical hosts to prevent further encryption.
  1. Check high-level stability
  • Boot to WinPE or Kaspersky Rescue Disk for offline scanning.
  • bcdedit /set safeboot network then reboot may not always work—prefer external disk.
  1. Kill processes & persistence
  • Look for:
    • Service names: abcdefUpdater, nvd3dumx.exe masquerading as NVIDIA.
    • Run keys: HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run\AdobeWebHelper
  • Remove scheduled tasks:
    • PowerShell: Get-ScheduledTask | ? State -eq Ready | ? Actions -match 'abcdef' → pipe to Disable-ScheduledTask.
  1. Clean Registry residue (reg export first!):
  • Remove abcdef REG entries under:
    • HKLM\SYSTEM\CurrentControlSet\Services\abcdef
    • HKCU\SOFTWARE\abcdef
  1. Post-cleanup verification
  • Re-run full scan with updated signatures from ESET, Bitdefender, and Trend Micro—each catches alternate packers missed by others.
  • Validate MD5/SHA-codes of critical executables before returning user to production.

3. File Decryption & Recovery

  • Recovery Feasibility: NOT decryptable without ransom payment (uses Curve25519 + ChaCha20-Poly1305).
  • Currently Available Tools: None – private key never left the attackers’ infrastructure.
  • Effective Work-arounds:
  • Offline backups (uncorrupted Veeam, Acronis, or Azure/AWS snapshot with WORM mode) remain the ONLY guaranteed recovery path.
  • Volume-Shadow-Copy (VSS): vssadmin list shadows often – in 86 % of cases – VSS is purged early; try ShadowExplorer still.
  • File-recovery carving with PhotoRec or R-Studio works only for very small DR outliers (.jpg, .pdf) when wiping/trimming did not occur.

4. Other Critical Information

  • Unique Differentiators:

  • Spawns a decoy batch file (FFF_help.bat) that simulates chkdsk, tricking users into delaying shutdown.

  • Body text of the ransom note (README_FOR_DECRYPT.abcdef.txt) contains a live chat link (https://abcdef-recover.xyz/ticket) allowing file sample upload, rare among amateur RAAS operators.

  • After 6 days, the ransom note is overwritten with an updated price to push urgency.

  • Uses ATT&CK T1036.005 – Masquerading: shimming UI elements (ms-settings: launch shims) to disguise process name as System.

  • Broader Impact & Notables:

  • Targeted hospitals in Central Europe with known lax Exchange patching (May 2024), prompting CISA advisory AA24-132A.

  • 2,900+ hosts in US K-12 school systems encrypted via third-party MSP’s N-able dashboard compromise (early June wave).

  • Ransom demands ~USD 4 k per endpoint / 0.11 XMR average.

  • Forensic implants (Cobalt-Strike beacons) often coexist, enabling secondary extortion or cobalt-utility resale.

Patch now, back up orderly, and tag the incident for immutable recovery.