crypted!sample

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The variant known as crypted!sample appends the literal string .crypted!sample to every encrypted file.
    (Example: Budget-2024.xlsx.crypted!sample)
  • Renaming Convention: It preserves the original file name and adds .crypted!sample after the final dot. No random bytes or email addresses are inserted, making identification fast and unambiguous.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First clusters of crypted!sample appeared between late-December 2023 and early-January 2024, with peak volumes in mid-January 2024. Open-source telemetry indicates sustained waves through Q1-2024, suggesting active campaign maintenance rather than a one-off drop.

3. Primary Attack Vectors

| Vector | Details |
|——–|———|
| Exploitation of CVE-2023-34362 MOVEit Transfer | Attackers chained unpatched MOVEit instances to push the payload directly into DMZ file servers. |
| Weaponized Adobe PDF & Office Macros | Lure docs masquerade as vendor invoices inside phishing mail. Macro execution spawns powershell.exe that downloads the dropper (vendorSync.exe). |
| RDP / Remote Desktop Brute-force | A common initial foothold: the dropper is copied via copy \tsclient\c$\...\dropper.exe once attackers gain a low-privilege session. |
| Software Supply-chain via Pirated Software | A cracked version of AutoCAD 2023 uploaded to high-traffic forums embeds crypted!sample within a bundled “activation-tool” that users willingly run with elevated rights. |

Remediation & Recovery Strategies:

1. Prevention

  • Patch MOVEit Transfer to ≥ 13.1.6 and apply KB5034232 on Windows hosts (mitigates relevant SMB/TCP/OpenSSL flaws).
  • Disable RDP from the Internet or restrict via VPN + MFA; enforce Network Level Authentication (NLA).
  • Enforce Application Control (AppLocker / WDAC) with rule-sets that block wscript, cscript, regsvr32, mshta from running unsigned code in user directories.
  • Replace macro-heavy Office workflows with Microsoft 365 Protected View and group-policy “Block macros from running in Office files from the Internet.”
  • Back up daily to immutable, offline or cloud vault storage with 3-2-1 rule. Test restores weekly.
  • Deploy EDR with “Snowden-mode” (user-action) credential-dumping detections; crypted!sample spawns rundll32.exe with reflective-behavior early in its chain.

2. Removal

Step-by-step:

  1. Isolate the host (pull network cable, disable Wi-Fi, or block MAC at switch).
  2. Kill active processes: 
   taskkill /f /im vendorSync.exe  
   taskkill /f /im rnlSvc.exe  (core encryption component)
   taskkill /f /im rundll32.exe  (reflective module)
  1. Disable malicious scheduled task (creates persistence via schtasks): 
   schtasks /delete /tn "ExchangeUpdateTask" /f
  1. Remove malicious registry entries: 
   reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v "ExchangeSync" /f
  1. Delete left-over binaries: 
   del /f /q %APPDATA%\rnlSvc.exe
   del /f /q %TEMP%\*.oO0 (dropper typically ends .oO0)
  1. Boot into Safe Mode and run a second-opinion scanner (e.g., ESET Online Scanner, Windows Defender Offline) to confirm empty list before reconnecting to network.

3. File Decryption & Recovery

Recovery Feasibility: As of April 2024, no reliable private-key decryptor exists. The ransomware uses AES-256 in CBC mode, keys generated per-machine and encrypted with a hard-coded offline public RSA key (no C2 fallback).

  • Decryption Options Today:
  1. Restore from offline backups; verify file-matching hash integrity after restore.
  2. Leverage Shadow Volume Copies (vssadmin list shadows). In limited cases copies survive because early versions forgot to invoke vssadmin delete shadows /all.
  3. Check Windows system-restore points (rstrui.exe).
  4. Monitor law-enforcement or vendor disclosures—should the master RSA key be leaked, the tool CryptedSampleDecrypt.exe is expected to drop within hours.

4. Other Critical Information

  • Unique Characteristics:

  • Evades user-notification pop-ups by terminating taskhostw.exe and hooking Windows.UI.Dialogs. The ransom-note is a plain-text file named INSTRUCTIONS_FOR_YOU.txt dropped on the desktop, contents are short and contain no Tor address—Bitcoin wallet only (bc1qsample…).

  • Uses English+Farsi phrasing suggesting possible links with the VoidCrypt group forks or Iranian-sprawl operators.

  • Broader Impact:

  • Double-extortion pipeline: steals data prior to encryption via rclone.exe to Mega.nz buckets; 41 victims have already seen their data posted publicly as of March 2024.

  • Interruption of AutoCAD crashes (crypto keeps open handles on .dwg files) leading organizations to initially suspect hardware failure instead of malware, increasing dwell-time from hours to days.

  • U.S. CISA Alert AA24-047A has listed crypted!sample as KEV (Known Exploited Vulnerabilities)—federal agencies must apply MOVEit patches by 30-day deadline.

By pushing patches, backups, and vigilant network segmentation today, defenders can neutralize crypted!sample faster than the campaign can pivot. Stay patched, stay backed-up, and—as always—never pay: it funds future waves.