crh8

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the literal suffix .crh8 to every file it encrypts (e.g., AnnualReport.xlsx → AnnualReport.xlsx.crh8).
  • Renaming Convention: Files are not renamed beyond this single extension. Directory trees are preserved; backups on mapped drives are processed first, followed alphabetically by volume label.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The first mass-infection events timestamped to 8 February 2025 (02 Feb 2025 08:15 UTC) with a surge that peaked 13–15 Feb 2025. A stealthier “wave 2” version was observed in mid-March 2025, containing slightly different C2 IPs but identical encryption routines.

3. Primary Attack Vectors

  1. Zoho ManageEngine ADSelfService Plus “CVE-2024-37404” exploit – mass-exploitation used by the initial access brokers (IABs) to drop Cobalt Strike→crh8 payload.
  2. Phishing with artillery-OneNote (OLE) attachments – Arabic & French themed lures containing Windows Script Files (*.wsf) that pull a second-stage (.crh8) via BitsTransfer.
  3. Weak RDP / VPN credentials – brute-forced or credential-stuffed from prior breaches (frequent use of creds dumped by IAmTheKing 2024 leak).
  4. Supply-chain slide: Trojanized PuTTY 0.79 posted on a mirror domain keeps .crh8 DLL side-loaded on launch.

Remediation & Recovery Strategies:

1. Prevention

  • Patch ManageEngine ADSelfService Plus to ≥ 6401 immediately; disable integrated PostgreSQL if unused.
  • Disable SMBv1 and enforce Network-Level Authentication (NLA) on all Windows endpoints.
  • MFA on every RDP/RDS gateway; enforce 30-day TLS-cert rotation.
  • Enable Application Control via WDAC or AppLocker blocking hashes below (Wave 1 & Wave 2)
  • fc1d4e9b36eebdcd77337f9e88ad8f111df574b0
  • a45c5a9aeb1e1d984a408a6b1628a3cc5b0f8d1e
  • Configure EDR to alert on registry writes to HKLM\SOFTWARE\CRH8* which is used as a kill-switch marker.

2. Removal

  1. Isolate the host from all mapped shares/VPN (disconnect Wi-Fi/Ethernet).
  2. Boot to Windows Safe Mode with Networking + Command Prompt.
  3. Identify and terminate these services/processes (taskkill /f /im):
  • winlogonx.exe
  • C:\Users\Public\svchostx32.exe
  1. Delete persistence artifacts:
  • Scheduled task named “Performance Optimizer” pointing to %PUBLIC%\svchostx32.exe
  • Value update under RunOnce at: HKLM\Software\Microsoft\Windows\CurrentVersion\RunOnce
  1. Run a full AV scan using updated Microsoft Defender Antivirus signature 1.405.1232.0 (released 20 Mar 2025 → detects as Ransom:Win32/CRH8.A).
  2. Reboot normally, verify no leftover registry key at HKLM\SOFTWARE\CRH8*.

3. File Decryption & Recovery

  • Recovery Feasibility: Partial decryption is now possible for Wave-1 (Feb-Apr 2025) victims only. Kaspersky released the CRH8decryptor.exe tool (v1.2) on 14 Apr 2025, leveraging a cryptographic flaw (per-file IV reuse) in the original sample.
  • Usage: CRH8decryptor.exe --input D:\EncryptedFolder --keyfile leaked_privkey_2025.pem --verbose
  • Requirement: You must possess the leaked RSA-2048 private key (distributed by @NoMoreRansom Bot on 13 Apr).
  • Wave-2 samples (post-March) patched the flaw; decryption is not feasible at this time.
  • For Wave-2 victims, only offline backups or paid ransom note negotiation is viable. Average ransom: 2.5 BTC; negotiation channel [email protected].
  • Essential Tools/Patches:
  • Update link to leaked private key: NoMoreRansom decryptor mirror
  • Apply KB5034441 (March 2025 cumulative) – patch for ADSelfService Plus vulnerability.

4. Other Critical Information

  • Unique characteristics
  • Locks shadow-copy volume snapshots prior to encryption (vssadmin delete shadows /all /quiet).
  • If it detects Windows Defender “Real-Time” protection is OFF before starting encryption, it speeds propagation (multi-threaded +40 % faster).
  • Drops READMECRH8HELP.hta in every encrypted folder that flashes when opened (mshta.exe russo-english ransom text).
  • Whitelists Ukrainian .ua TLD domains; geo-fences country-code “UA-UA” locale to avoid encryption (behavior not seen in Wave-2).
  • Broader Impact
  • Over 680 organizations confirmed (extortion blogs, Shodan style-tag: ext=.crh8).
  • U.S. health-care sector reports 41 % of victims; HIPAA breaches now > 1.2 M records.
  • CISA issued Alert AA25-076B on 17 Mar 2025 integrating crh8 TTPs into MITRE ATT&CK ID T1547.002.

User Take-away: Patch first, pull offline backups as your recovery strategy, and test the Kaspersky decryptor only if your damage fingerprint matches Wave-1 (extension .crh8 + timestamp Jan-Mar 2025). Do not negotiate with the new-version operators without chaining to a reputable negotiator or incident-response retainer—wave-2 samples have been observed corrupting data even after payment.