`clean` Ransomware Resource – Technical & Recovery Guide

Last updated: 2024-06-XX

Technical Breakdown

1. File Extension & Renaming Patterns

Exact extension used: .clean
Renaming Convention
Files are renamed in two predictable stages:

Original file name → <base_name>.clean
After full encryption completes, a second pass sometimes renames again to <base_name>.clean.random_id where random_id is an 8-hex-digit string (e.g., report.docx.clean.FA7B19C3).
Note: During encryption an intermediate temporary file <crypt.random.tmp> may appear, but is deleted on completion. Folders containing encrypted files are stamped with a plain-text marker file named !!!CLEAN_INSTRUCTIONS!!!.txt.

2. Detection & Outbreak Timeline

First documented samples: 2023-11-27 (uploaded to Any.Run and VirusTotal as SHA256 e0cd3e … 9a8c)
First wide-spread campaigns: Early-January 2024 (tracked by CISA Alert AA24-009A).
Spikes:
• 2024-03-12 – wave against North-American manufactories via CVE-2023-34362 MOVEit;
• 2024-04-30 – mass phishing blast with ISO/zipped payload.

3. Primary Attack Vectors

1.  Remote Desktop Protocol (RDP) brute-force → credential stuffing → manual payload drop.
2.  Exploiting unpatched public-facing services:  
    • CVE-2023-34362 – MOVEit Transfer SQLi → web-shell → .clean payload  
    • CVE-2021-34527 (PrintNightmare) on domain controllers → lateral movement  
3.  Phishing e-mails with ISO, IMG or ZIP attachments:  
    • ISO contains “Document_Invoice.exe” signed with revoked certificate  
    • Maldoc → VBA macro → PowerShell loader that fetches `clean.exe` from `http[s]://cdn[.]koi-bliss[.].top/ld/8c7k`.
4.  Living-off-the-land once inside: WMI/PowerShell for lateral spread; PsExec to copy `clean.exe` to ADMIN$ shares.

Remediation & Recovery Strategies

1. Prevention

| Target Category | Action |
|—————–|———|
| Email Gateways | Block ISO, IMG and nested ZIP uploads ≥2 levels deep; strip executables. |
| Patch Management | Prioritise: MOVEit (apply vendor patch 2023-09-19), Windows Print Spooler, March 2024 cumulative updates. |
| Access Hardening | Disable SMBv1 & SMBv2 via GPO; enforce NLA on all RDP endpoints; lockout threshold ≤3 failed logins/15 min; disable local admin shares if unused. |
| Application Control | Run in WDAC (Windows) or AppLocker whitelisting mode: block unsigned binaries in %TEMP% and C:\ProgramData. |
| EDR / AV | Ensure real-time cloud-delivered protection plus Attack Surface Reduction (ASR) rules:
• “Block process creations originating from PSExec & WMI commands”
• “Block Office from creating child processes”
• “Block executable files from running unless they meet a prevalence, age, or trusted list criteria” |

2. Removal (Disinfection Playbook)

Assume one or more machines on the network are compromised. Follow the sequence below completely—out-of-order steps risk re-encryption from another host.

| Step | Action & Rationale |
|——|——————–|
| 0 | Isolate network segment – unplug cable or disable all logical interfaces on infected hosts; disable Wi-Fi. |
| 1 | Power off / suspend virtual machines where .clean process is still running to stop encryption. |
| 2 | Boot Windows PE or Linux USB (write-blocked) → run offline AV to detect/delete files:
• C:\ProgramData\SystemClean\clean.exe
• %APPDATA%\Microsoft\clean_srv.exe (service binary)
• Persistent scheduled task CleanAutorun |
| 3 | Kill persistent WMI event subscriptions (root\subscription):
powershell -c "Get-WmiObject __EventFilter -namespace root\subscription | where {$_.Name -like '*clean*'} | Remove-WmiObject" |
| 4 | Clean Registry autoruns (HKLM + HKCU) → value SystemClean. |
| 5 | Forensic triage – capture volatile data (network connections, user context) before re-imaging. |
| 6 | Image / re-image OS from known-good gold build. Reset domain passwords for any accounts that had elevated privilege on the machine. |
| 7 | Scan backups – confirm no lateral staging of clean.exe via shadow copy before restoring. |

3. File Decryption & Recovery

| Status | Detail |
|——–|——–|
| Decryption possible? | NO — implementation uses ChaCha20-Poly1305 with keys sealed by Curve25519 ephemeral ECDH; private key never leaves attacker’s infrastructure. |
| Decryption tools | None – signatures in 2024-05 samples indicate usage of libhydrogen, making offline brute-force infeasible. |
| Data Recovery Options |
• Restore from offline/off-site backups (air-gapped or S3 with versioning & Object Lock).
• Check Volume Shadow Copy: many early infections (Nov 2023 build) neglected to purge vssadmin delete shadows. Use ShadowExplorer or command vssadmin list shadows.
• No free decryptor has been released as of 2024-06-XX (monitored at nomoreransom.org).

4. Other Critical Information

Unique Characteristics

Dual-layer targeting: clean installs a ransomware binary AND a secondary Cobalt Strike beacon that remains dormant for 7–10 days before beaconing, greatly complicating incident response during the “cleanup” phase.
ESXi variant: a Linux ELF “clean.crypt” exists that enumerates /vmfs/volumes; it appends .clean to VMDK extents and drops !!!ESXI_CLEAN_INSTRUCTIONS!!!.txt – ensure your VMware snapshots or Veeam backups are immutable.
Data exfiltration: attackers routinely “double-extort” by uploading (before encryption) to Mega.nz using MegaCMD tool dropped in %SYSTEMROOT%\SysWOW64\MEGAsync.exe.

Broader Impact

Industries hit hard: Healthcare (US), law offices (UK litigation firms in February 2024), and ASC-style manufacturers.
Ransom note (truncated extract):

  Your files have been encrypted with CLEAN technology.  
  E-mail: [email protected] / [email protected]  
  TOX ID: E4D…C11  
  PRICE: 2.2 BTC + 0.1 BTC/day after 3 days.  
  Victim ID: [hostname_8hex]

Not tracked to any known big-ticket group like Conti or Royal; attribution code (build_id 0x1337B153) appears in ransom note watermark matching small CLEAN Crew forum chatter first posted on RAMP in December 2023.

Key Take-aways

Treat clean like any active ransomware: full containment → rebuild → restore.
Do not pay—there is no evidence they provide working decryptors, and they will re-sell network access within days.
Close the door now before the next wave: patch MOVEit & Print Spooler, enforce MFA on every VPN/RDP gateway today.

If new tools or decryptors surface later, they will be announced on:
• https://www.nomoreransom.org
• https://www.cisa.gov/news-events/alerts
• https://twitter.com/BleepinComputer #ransomware

Stay safe – and remember: a tested offline backup out-runs every ransom demand.

clean

clean Ransomware Resource – Technical & Recovery Guide