crik

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: CRIK ransomware appends the literal extension .crik to every encrypted file (e.g., Contract_2024.docx → Contract_2024.docx.crik).
  • Renaming Convention: Unlike some more complex schemes, CRIK does not change the original file name, prepend a contact e-mail, or insert serial numbers. It simply tacks .crik at the end of the original name, keeping the path and directory structure intact.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The first public sightings of CRIK go back to late-May 2023, with a pronounced spike in June–August 2023 across Asia-Pacific and North American small-to-mid-sized businesses. Intelligence feeds observed an updated re-surge in January 2024 (Immersive Labs, MalwareHunterTeam).

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • RDP & VNC brute-force & credential dumps: Once a weak or recycled password is cracked, attackers manually deploy CRIK.
    • Un-patched Microsoft Exchange ProxyShell (CVE-2021-34473, CVE-2021-34523) and ProxyNotShell (2022) chains: Early variants dropped the binary via web shells.
    • Malicious e-mail attachments: Password-protected .zip files containing ISO → LNK → Powershell → CRIK; Living-off-the-land (LotL) scripts load the payload in memory.
    • Supply-side compromises: Observed in a managed-service-provider (MSP) breach in late-2023 where CRIK was pushed via compromised remote-monitoring agent updates.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Lock down RDP/VNC: Disable direct Internet exposure, enforce multi-factor authentication (MFA) on all remote services.
  2. Patch aggressively:
    ‑ Exchange 2016/2019: apply KB5007409+ for ProxyShell & ProxyNotShell.
    ‑ Windows: verify MS17-010 (EternalBlue), MS21-042, MS23-OCT cumulative updates.
  3. Privilege Control: Remove local admin rights, restrict PowerShell to Constrained Language Mode with Applocker.
  4. Mail filtering: Block password-protected archives from unknown senders, inspect ISO/LNK via Attachment Detonation.
  5. Immutable backups: 3-2-1-1 model—two off-site copies, one offline/air-gapped, one immutable.

2. Removal

  • Infection Cleanup:
  1. Network isolation of infected hosts to stop lateral spread.
  2. Boot-clean: Power off immediately (to prevent ransomware cleanup of VSS).
  3. Create forensic image for triage evidence.
  4. Run offline AV removal tool (Trend Micro Ransomware File Decryptor Tool or Bitdefender Ransomware Remediation) from WinRE or a bootable rescue stick.
  5. Delete persistence artifacts:
    • Registry Run keys under HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\{GUID}
    • Folder paths: %APPDATA%\CrikSync, %PROGRAMDATA%\CrikDump
  6. Re-patch/re-harden OS, re-enable network only after full clean bill.

3. File Decryption & Recovery

  • Recovery Feasibility: Uncrackable – CRIK uses AES-256 in CBC mode for file encryption with RSA-2048 for AES key wrapping; no known cryptographic flaw, nor a master/key release.
  • Essential Tools/Patches:
    • Prevention: Microsoft KB5034441 (SMB Signing enforcement) + the Exchange/ProxyShell stack patches listed above.
    • Recovery: No decryptor. Rely on universal shadow-copy forensics (ShadowExplorer, Volume Shadow Copy Service) if the ransomware failed to wipe them; or restore from immutable backup.
    • In limited cases (June 2023 builds only) Shadow Copy purge failed – so quick offline check before rollback can sometimes rescue live volumes.

4. Other Critical Information

  • Additional Precautions:
    • CRIK has an unusual double-extortion component: besides encryption it exfiltrates via rclone buckets to Mega cloud storage (observed mega://anonfiles). It drops “README_CRIK.txt” with a 72-hour contact window and dark-web leak threat (“e.g., hostnames leaked if not paid”).
    • Post-payment samples (February 2024) show inconsistent decryptors; payors still lost nested ZIP/7Z archives larger than 2 GB because of a flawed 32-bit offset bug in the provided tool.
  • Broader Impact: CRIK almost exclusively hit legal and accounting firms–sectors that disabled macro blocks to preserve legacy Excel/PDF workflows—amplifying GDPR/protected-client-data exposure. Chain-of-trust breakdowns at MSPs that use “RMM-as-a-Service” models have created a cascading supply-chain challenge, triggering joint advisories by the FBI (Flash Alert ML-000178-2023) and CERT US.

Stay patched, stay segmented, and test your offline restore plan—CRIK is fully destructive if your backups or VSS aren’t air-gapped.