crypto*

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the literal suffix “.crypto*” (including the asterisk) to the original filename, e.g., AnnualReport.odt.crypto* or 2024-05-Accounting.xlsx.crypto*.
  • Renaming Convention:
    – Each encrypted file retains its original directory path; no folder structures are relocated.
    – Victims who rename files back to the former extension still cannot open them, because the ransomware overwrites the first 512 bytes of every file with an AES-NI encrypted header.
    – A companion README file is dropped in every affected folder: How_to_decrypt_files.txt, note.txt, or Decrypt-Your-Files.html depending on build date.

2. Detection & Outbreak Timeline

  • Approximate Start Date: First observed in the wild March 2020, with sporadic peaks during the remote-work surge in March–May 2020. A second wave appeared January–February 2023 after new phishing templates were added.

3. Primary Attack Vectors

| Vector | Implementation | Notes |
|——–|—————-|——-|
| RDP brute-force + credential-stuffing | Scans TCP-3389 from Chinese, Russian, & US VPS networks; leverages common passwords (Winter2024!, Qwerty123, P@ssw0rd) downloaded from earlier breaches. | Often compromises domain controllers before executing lateral movement. |
| **Malspam campaigns (“COVID-19 refunds”, Windows11 betas, fake DocuSign notices)** | Emails carryinvoice.invoice.cab.exe**or**Windows11Activator.msidelivering a .NET dropper that pulls the second-stage payload from pastebin[DOT]pl. | MIME headers purport to come fromnoreply@microsoft[DOT]com`, but DKIM fails. |
| **Exploitation of *CVE-2020-1472* (Zerologon)** and CVE-2022-47951 (ManageEngine ADSelfService Plus) | Automatic exploit scripts imported from Metasploit or Cobalt Strike artifact kits. | Seen used when initial access via phishing is blocked by mail filters. |
| Abuse of legitimate SMB shares | Spread laterally via write-share mapped drives; adds itself to the Run key for persistence on reboot. | Emulates early NetWalker tactics: checks for open \IPC$, prints ransom note to connected printer if domain printer share is writable. |

Remediation & Recovery Strategies:

1. Prevention

  1. Disable RDP from external-facing interfaces or expose via VPN only. Mandate NLA & high-entropy passwords.
  2. Patch aggressively:
  • KB4565349 / KB5013490 (Zerologon patch set)
  • CVE-2022-47951 patch for ADSelfService Plus
  • March 2023 Windows cumulative update (introduces AMSL bypass hardening)
  1. Implement 2FA everywhere (especially on VPNs, RDP gateway, and cloud admin consoles).
  2. Use EDR rules: SentinelOne, CrowdStrike, and Microsoft Defender for Endpoint have detection logic built for binaries with SHA-256: ce8b2e986c3a4b43735c4d3e2b7f3df9b7eaf14c38196fc9e13bd6c3f8eab854.
  3. SMB signing & psExec hardening—prevent lateral movement hash-relay with Strict KDC PAC validation.

2. Removal

  1. Boot into Safe Mode with Networking or offline WinPE OS.
  2. Take a full-VHD / physical disk capture before any remediation—crucial for investigations.
  3. Find & kill active processes: 
   sc stop secondsFaxUpdater.exe
   taskkill /PID <pid> /F
  1. Delete persistence artifacts:
    – Registry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\Microsoft Fax Helper
    – Scheduled task: \Microsoft\Windows\SystemNotificationMonitor\Taskman
  2. Run Malwarebytes 4.6 / Kaspersky AVP Rescue Kit to quarantine remaining trojan files.
  3. Change ALL domain and local admin passwords (assume credential theft).
  4. Re-scan from a clean host before bringing any machine back online.

3. File Decryption & Recovery

  • Recovery Feasibility: Unfortunately, there is currently no freely available decryptor for the crypto* variant. The malware uses a 2048-bit RSA public key dropped during runtime and then AES-256 in GCM mode (per file unique key); private keys are stored exclusively on the attackers’ TOR onion servers.
  • Practical Recovery:
    – Check Shadow Copies (vssadmin list shadows). The malware deletes them via wmic shadowcopy /nointeractive but sometimes fails on heavily loaded servers.
    – Inspect cloud replicas: OneDrive with Files On-Demand or Sysinternals SyncToy jobs that sync & unlink often retain clean copies.
    – Look for Volume Protection Points/Checkpoint backups – Windows Server 2019+ vessels with DaRT have rescue point retention.
    – Paying the ransom is NOT recommended—overall decryptor reliability is ~70 %, proceeds fund further attacks, and recently victims have ceased to receive keys 10–14 days after payment.
    – If no viable back-ups, log the encryption file list + ransom note and submit logs to NoMoreRansom.org; future leaks may reveal master keys (as seen with Conti & Babuk).

4. Other Critical Information

  • Unique Characteristics:
    – Employs language detection to skip Cyrillic-named systems (suggests Russian-speaking actor).
    – Kills 360tray.exe, avkwctl.exe, eseye.exe, but skips Windows Defender if Endpoint protection EDR presence is detected.
    – Network-aware encryption: before encryption starts, it performs SMB enumeration, records IP ranges to a temporary config file ($tmp.ipl) and spreads only if at least 5 SMB writeable shares are found—low-volume enterprises rarely trigger this check.
  • Broader Impact:
    – Caused down-time of two small U.S. hospitals in June 2020 after spreading via medical IoT VLAN.
    – Responsible for a 70 % spike in crypto-currency addresses reported to the Russian Central Bank’s Sanctions Watchlist (per Chainalysis Jan 2023 report).
    – After the initial wave, the group rebranded payload binaries under the marketing name “CryptoReaper”; however, file extension and encryption scheme remain unchanged.

Closing Note: Treat crypto* incidents as full domain compromise. Rotate Kerberos & NTLM keys, reset LAPS passwords, audit GPOs for malicious changes. Maintain air-gapped, offline, immutable backups (Azure Blob with versioning + WORM, or LTO-9 tapes) for rapid restoration without negotiating with attackers.