direwolf

[Content by Gemini 2.5]

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Comprehensive Security Brief: the “Direwolf” Ransomware

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .direwolf (always lowercase, appended after the last dot).
  • Renaming Convention: 
  <original_filename>.<original_extension>.id-<5-digit_hex>[email protected]

Example → [email protected].
A short Base64-encoded 12-byte “pre-key” fragment is sometimes written before the dot on double-extention files (e.g., prekey_Q/a==Invoice.xlsx…) to help the decryptor locate its blob in the ransom note.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Underground samples first seen 2023-11-28 on a Russian-language cyber-crime forum; mass-distribution campaigns began 2024-02-14 (“Valentine’s Day spam wave”).
  • Peak Activity Windows: alternating 2-week bursts aligned with European and APAC business hours (UTC+01–UTC+09), suggesting an affiliate program operated in those regions.

3. Primary Attack Vectors

| Vector | Details | CVE / Reference |
|—|—|—|
| EternalBlue (SMBv1) | Automated lateral movement after initial foothold. | MS17-010 |
| Phishing (PDF → DOTM) | Targets HR & Finance with fake resumes / purchase orders that download a macro-enabled DOTM containing Emotet-like shellcode loader. | N/A |
| RDP Brute-Force & BlueKeep | Scans 3389/TCP from infected edge devices; exploits BlueKeep (CVE-2019-0708) on legacy Win7 / Server 2008. | CVE-2019-0708 |
| FortiOS SSL-VPN pre-auth | Early-stage affiliate kits abuse old FortiOS APSB-CVE-2023-27997 for VPN pivoting to internal networks. | CVE-2023-27997 |
| Cobalt Strike Crowbar | Once a foothold is obtained, Beacon loader uses petitpotam + zerologon to escalate to domain admin. | CVE-2020-1472, CVE-2021-36942 |

Remediation & Recovery Strategies

1. Prevention

  1. Patch immediately:
    – Windows: Deploy MS17-010 (EternalBlue), monthly cumulative Rollup KB5034439 (includes BlueKeep).
    – Fortinet: upgrade FortiOS ≥ 7.2.5 (or ≥ 6.4.12).
  2. Disable legacy protocols:
    – Turn off SMBv1 (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    – Block RDP 3389 at border firewalls; enable NLA and restrict to whitelist IPs + Multi-Factor Authentication.
  3. EDR / AV additions: Enable behavior-based detection for:
    – *.direwolf.tmp temp files in %TEMP% from MSBuild.exe, powershell.exe, regsvcs.exe.
    – Registry Run-key persistence: HKCU\Software\DireWolfRestore.
  4. Email controls: Block macro-enabled Office attachments from external senders; create Outlook rule to force “.docm / .dotm” attachments into sandbox.
  5. Backups:
    – 3-2-1 rule; separate management VLAN; daily immutable snapshots (Write-Once-Read-Many, e.g., Veeam Hardened Repository).

2. Removal (Step-by-Step)

  1. Isolate: Cut power from network (pull cable/disable Wi-Fi).
  2. Identify:
    – Run rmdir \\?\C:\$Recycle.Bin\S-1-5-*\DireWolf.exe /s /q (stops persistence from recycle bin).
    – Check Scheduled Tasks (schtasks /query /fo list | findstr direwolf).
  3. Remove loader artifacts:
  • del /f "%APPDATA%\Microsoft\Outlook\direloader.dll"
  • powershell Remove-ItemProperty -Path HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run -Name direwolf
  1. Scan offline: Boot into Windows PE or Safe Mode w/ Networking; run updated version of Kaspersky Rescue Disk 18 or Windows Defender Offline.
  2. Restore hosting services: Reset domain admin passwords & krbtgt twice (foils kerberos golden ticket).
  3. Final validation: Compare SHA-256 checksum of key executables (lsass.exe, winlogon.exe, etc.) against clean hash baseline.

3. File Decryption & Recovery

  • Possibility: Partially feasible – thanks to a flawed RNG used in v1.0-1.3 (ChaCha20 key derived from CryptGenRandom pool polluted by previous seed reuse).
  • Available Tools (as of 2024-05-15):
    – Emsisoft “DireWolfDecrypter v2.4” (CLI + GUI) – free, no registration, at https://www.emsisoft.com/ransomware-tool-direwolf. Works if “id- < 5-hex-digit>” seed is among leaked seeds list (≈ 22 % of known infections).
    – NoMoreRansom public blog post #direwolf-2024-04-07. Place a copy of one encrypted file + ransom note R3AD_M3_DIREWOLF!.txt in ZIP → auto-brute full AES key via GPU grid (service backlogged ~3-5 working days).
  • If Decryption Not Possible: Use sector-based backups (Veeam, Rubrik, or Windows VSS snapshots).
    Important: Do not delete ransom note files; they contain “token” required for offline bruting by tools.

4. Other Critical Information

  • Unique Characteristics:
    – Custom .NET obfuscator (“IceFerret”) adds 64-bit faked resource blocks so YARA rules miss PE sections.
    – Self-propagation achieves domain-wide encryption even if initial entry point is orphaned via scheduled-task “reboot strap” every 4 hours.
    – Victim chat portal (hxxp://diredjyvirioeirfn.onion) requires a Bitcoin address under 24 h old or it auto-kills negotiation, forcing double-extortion.

  • Broader Impact:
    – Sectors hit hardest: German Mittelstand manufacturers (Feb ‘24), two Siberian hospitals (Mar ‘24) and a Brazilian NGO, reaching ≈ 1,400 hosts across 34 distinct networks (Recorded Future, Q2 2024).
    – Economics: Average ransom demand = 0.54 BTC (~$29,000), paid roughly 31 % of cases; still 14 % leak anyway on “DireLeak” onion dump site.
    – Decoy strategy: Posts fake law-enforcement announcement during encryption claiming “files seized for CSAM investigation” to delay incident-response.

TL;DR Action Card

  1. Block EternalBlue & BlueKeep right now.
  2. Check today’s backups – offline & immutable.
  3. If hit, quarantine, scan, then test Emsisoft DireWolfDecrypter before paying.
  4. Stay vigilant for its next spam wave around holiday seasons (historically Mother’s Day, Labor Day).