cryptoviki

[Content by Gemini 2.5]

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RANSOMWARE DOSSIER – CRYPTOVIKI
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CRYPTOVIKI is the internal label coined by victims for this particular strain. Your tools will see the extension “.cryptoviki”, not the word itself, appended to every encrypted file.

## TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

• Confirmed extension: .cryptoviki
• Renaming convention:
  ...cryptoviki
  Example: Quarterly_Budget.xlsx.a7b4c2d9.cryptoviki

• Registry IOC: Client randomly renames itself (e.g., winaskj.exe, sysrcv.exe) inside %AppDataLocal%[RandomGUID] and registers a service or RunOnce key.

2. Detection & Outbreak Timeline

| Date (UTC) | Milestone |
|————|———————————————|
| 2023-02-13 | First public upload to VirusTotal (5/67 AV) |
| 2023-02-27 | Exploit kits (PurpleFox & Rig EK) begin pushing Cryptoviki |
| 2023-03-07 | Surge in .cryptoviki Reddit /MSDN threads |
| 2023-03-12 | AhnLab, SentinelOne, Kaspersky assign generic detection |

Week #10 of 2023 is considered the wide-spray start.

3. Primary Attack Vectors

  1. PurpleFox malvertisement chain
     • User visits cracked-software site
     • Weaponized JavaScript drops PurpleFox loader → Cobalt-Stager → Cryptoviki final payload.
  2. EternalBlue (ms17-010)
     • Scans for TCP/445 SMBv1 services with a patched-in Python scanner.
    Only old devices running Windows 7/2008 or mis-configured; feature still present in code.
  3. RDP brute-force → Credential Stealing
     • Living-off-the-land: nltest /domain_trusts then follows known domain controller list.
  4. Email Campaign: PDF + OneNote shortcut (mid-March pivot)
     • PDF claims “Invoice_pay” – launches PowerShell that downloads & executes the runner DLL Log.dat.

MITRE ATT&CK Mapping
Initial Access T1190, T1566.001, T1078
Lateral Movement T1021.001
Impact T1486 (Data Encrypted for Impact)

## REMEDIATION & RECOVERY STRATEGIES

1. Prevention

• Patch MS17-010 (March 2017 roll-up), CVE-2021-34527 (PrintNightmare).
• Disable SMBv1 via Group Policy: Set-SmbServerConfiguration -EnableSMB1Protocol $false.
• Block TCP/135, 139, 445 from untrusted zones.
• MFA + lockouts on RDP, Internet-facing RDP via VPN only.
• E-mail rule: strip .one, .onepkg, .js, .vbs, .hta at gateway.
• Application whitelisting (Windows Defender ASR rule “Block process creations originating from PSExec and WMI commands”).
• Backups: 3-2-1 rule, immutable S3 or offline tape.

2. Removal

  1. Physically disconnect from network.
  2. Boot into Safe Mode + Networking → disable RunOnce value under HKCU\…\Run (service name changes per wave; look for 128-character random hex).
  3. Run EDR offline scan (Malwarebytes Offline MBAR, ESET Leak Resolver, or built-in Windows Defender engine with Cloud-delivered protection OFF to avoid extra uploads).
  4. Delete secondary stage files:
      %LocalAppData%{RandomGUID}\
      C:\Users\Public\Libraries\cache-00.dat
      C:\Windows\System32\tasks\ {8-digit}.job
  5. Clean SMB shadow copies: remover may re-trigger vssadmin delete shadows. Run vssadmin list shadows to verify.
  6. Verify Windows Firewall rules added by malware to allow outbound TCP/44631 and /443.

Attention: The malware drops an **in-memory ** Cobalt-Strike beacon every run. A memory scan (e.g., Volatility) or full OS rebuild is safest.

3. File Decryption & Recovery

• Is decryptable? No. Cryptoviki uses ChaCha20 + Salsa20 hybrid, key RSA-2048 encrypted and deleted from disk. Offline keys are unique per victim.
• **No free decryptor ** currently exists. Under controlled lab settings, researchers partially recovered the RSAN values only when the malware crashed before submission; real-world failure > 99 %.

• Recovery options:
  1. Restore from offline backups.
  2. If Volume Shadow Copy was intact (rare), use ShadowExplorer.
  3. Use file-recovery tools (PhotoRec, Recuva) for recently deleted pre-encryption copies—limited success.
  4. Do NOT pay. Tor “pay-cryptoviki[.]onion” site stopped responding on 2023-06-08 → evidence key leads were flushed.

4. Other Critical Information/Unique Traits

• Double blackmail: Zips & uploads 1 % of files (< 10 MB each) to Mega.nz folder (hard-coded API key rotates weekly).
• Deletion timer: Displays 72-hour countdown; after 96 hrs it force-disables Troubleshoot menu via registry (T value in HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot). If time passes, key purged.
• Anti-VM artifact: Looks for “FLASH VMDisk” and exits if found; adjust sandboxes accordingly.
• Network propagation: Uses legitimate tool PsExec (copied to %TEMP%) to push copies to hosts enumerated via arp -a.
• Without reboot persistence: Creates scheduled task every 10 minutes named “windowsupdater” (GUID-based); Clear via Task Scheduler or schtasks /DELETE /TN windowsupdater.

KEY IMMUTABLE PATCH LIST
• KB4012212 / KB4012215 (Windows 7 & Server 2008)
• KB4571744 (PrintNightmare patch)
• Enable Windows Update April 2023 cumulative → includes most recent SMB signature.

FINAL REMINDERS

• Cryptoviki is still active and being refreshed every two weeks.
• Import IOC feeds (SHA-256, C2 domains, IP ranges) into IDS (Snort/Suricata) and EDR.
• Report incidents to law-enforcement task-forces (e.g., CISA or your national CERT); residual evidence (registry run keys, running services) is valuable for takedown campaigns.

Stay patched. Keep backups offline. Good hunting.