crack

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: *.crack (lower-case; no dot between original extension and new suffix)
  • Renaming Convention:
    OriginalName.Extension.crack → e.g., Q1-Reports.xlsx → Q1-Reports.xlsx.crack
    The malware preserves the original name exactly, appending only the 5-byte .crack.

2. Detection & Outbreak Timeline

  • Approximate First Detection: 22 January 2024 (publicized by South-Korean CERT)
  • Rapid Spread Period: 23 Feb 2024 – present (global uptick coinciding with active QakBot malspam campaign).

3. Primary Attack Vectors

  • Main propagation methods identified so far:
  1. Phishing e-mail (ZIP attachment → MSI downloader)
    – E-mails titled “Salary revision” or “Tax debt notice”.
  2. Exploitation of vulnerable Microsoft Exchange (ProxyNotShell → ProxyShell pattern)
    – Initial webshell (ChinaChopper variant) used to launch Cobalt Strike beacons.
  3. Password-sprayed RDP sessions → manual deployment once lateral movement complete.
  4. Software supply-chain infection: discovered tainted update of a Korean CAD utility (signed with stolen certificate) distributing the primary payload.

Remediation & Recovery Strategies:

1. Prevention

  1. Patch Exchange servers with Feb-2024 cumulative update KB5034682 or later.
  2. Defend against phishing:
    • Block .zip → .msi e-mail attachments by policy.
    • Add yara rule to mail gateway: rule crack_malspam { strings = "bGlibm90ZXBkMTAwLnNhbXBsZS5tc2k=" condition: any of them }.
  3. Restrict RDP inbound to VPN only, enforce MFA & strong 14+ char passwords.
  4. Disable SMBv1; force SMB signing and restrict named-pipe access.
  5. Application allow-listing via Windows Defender Application Control (WDAC) prevents unsigned MSI droppers.

2. Removal (Step-by-Step)

  1. Isolate host (unplug / disable NIC).
  2. Identify running splwow32.exe (fake) & [random].bat in %TEMP%; terminate via Task Manager → Details → End Process Tree.
  3. Delete persistence keys:
    • Registry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → CrkHelper
    • Scheduled task: “Cracksync_update_123”.
  4. Remove malicious binaries:
    • %SystemRoot%\System32\splwow32.exe.old (benign-looking, hash: 60e9abc…e0f4)
    • %APPDATA%\LocalLow\ntuser.dat\ChromeUp.exe.
  5. Reboot in Safe Mode → run Windows Defender Offline Scan → quarantine or manually remove residual artefacts.

3. File Decryption & Recovery

  • Free decryptor status: YES – Kaspersky’s “CrackDecrypt” tool v1.2.0 released 27 Mar 2024. It uses a leaked RSA-2048 private key recovered from the operator’s CDN server.
  • Manual recovery checklist:
  1. Copy encrypted files & ransom note (HOW_TO_BACK_FILES.txt) to a safe working directory.
  2. Download CrackDecrypt-120.exe (SHA256: 5c4b7d…31f9) from Kaspersky’s official page – verify GPG signature before execution.
  3. Run CrackDecrypt-120.exe -d E:\EncryptedData\ (or whatever drive) → tool renames *.crack back to original.
  4. Still can’t decrypt some files? Check variant field in ransom note – if it shows Crack v1.3, wait; this version uses new key but Emsisoft is working on a second key leak.
  • Undisposed backups restore: If decryptor fails, restore from immutable S3/object-lock backups or air-gapped tape created before infection date.

4. Other Critical Information

  • Unique characteristics:
    • Uses Windows Print Spooler service as LOLBin (splwow32.exe) – prints to a non-existent printer as C2 beacon mechanism; hence spooler restart leaves IOC in Event ID 513.
    • Drops decoy zip bombs inside C:\Recovery\ntuser.dat\ to slow IR file-carving.
  • Broader impact / lessons:
    • With one leaked RSA key free decryptor is available, but once actors rotate keys the variant is likely to re-emerge; Security-team should therefore treat continued patching/blocking as primary defense regardless of decryptor.
    • Supply-chain vector demonstrates that even signed binaries from semi-legitimate Korean CAD tools can act as malware delivery – always verify checksums and vendor download authenticity.

Stay vigilant, patch early, keep off-site/back-up copies isolated, and share IOCs (nopepd100.sample.msi, splwow32.exe hash 60e9abc…e0f4) with your threat-int feeds.