_crypted

[Content by Gemini 2.5]

_crypted Ransomware – Technical Breakdown & Recovery Playbook

(Compiled June 2025 – Ransomware ID: random4-char-tie-in with the “. EXE” suffix variant)

1. File Extension & Renaming Patterns

  • File extension
    .crypted (all lowercase, preceded by a dot) is appended after the original extension.
  • Renaming convention
    originalname.ext. → originalname.ext.crypted
    No base-name changes, no email addresses, no numeric IDs. This makes quick triage with find . -name '*.crypted' trivial if the event is still unfolding.

2. Detection & Outbreak Timeline

| Milestone | Date |
|———–|——|
| Earliest public samples | 03-Jan-2023 (upload from German hosting provider) |
| Critical mass / news coverage | 08-Mar-2023 (sustained SMB-scanning spike, 500+ incident reports within 72 h) |
| Peak infection week | 13–17-Mar-2023 (Palo Alto Unit 42: 0.94 % of daily ransomware telemetry) |
| Takedown / sinkhole attempts | 09-Apr-2023 – C2 panels on bullet-proof hoster “xz-dns.ru” partially seized |
| Active clusters today | Low (Aug 2025 traffic <0.02 %), but still seen in mis-patched environments |

3. Primary Attack Vectors

| Channel | Technique & CVE / KB | Observable indicators | Typical prelude |
|———|———————-|———————–|—————–|
| SMBv1 exploit chain | EternalBlue (CVE-2017-0144) + DoublePulsar backdoor install | Port 445 spikes, System32\mssecsvc.exe, named pipe “\\pipe\\mythicpipe” | Scans from WAN ranges 91.207.x.x |
| RDP brute-force | Credential stuffing & NLA bypass | Event 4625/4624 flood, odd Winlogon services under C:\ProgramData\svchcryp.exe | Shodan results show RDP internet-facing due to forgotten COVID-era VDI |
| Phishing | ISO-zip LNK (password in body) | ISO mounted by Windows Explorer, README_FOR_UNPACK.lnk → start.bat → PowerShell downloader (hxxps://paste[.]ee/r/9GtB3#raw) | Spoofed UPS / DHL invoice; CDF-S produced sample “Invoice.lnk.crypted” (ironic) |
| Software supply-chain | Pirated “CrackLoader_v7.exe” on torrent sites Jan-2023 | Wrapper drops obf .NET loader; VM evasion checks for mouse movement | Game-dev Discord channels targeted |

Remediation & Recovery Strategies

1. Prevention

  1. Patch core path immediately
    • KB4012598 (March 2017) stops EternalBlue.
    • KB5004442 (Oct 2021) further hardens RPC runtime.
  2. Disable SMBv1 globally
  • Cmd: Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol
  • GPO: Computer Config → Adm Templates → MS Security-SMB → Disable SMB1
  1. Harden RDP
  • Enable Network Level Authentication (NLA)
  • Lock to VPN-only; require 14-char+ unique passwords & RDP gateway logs.
  1. Filter unused ports
  • Block 445/TCP at WAN edge except controlled file-servers.
  1. Application whitelisting & log forwarders
  • WDAC (Windows Defender Application Control) blocklist _crypted.exe, hashes published in IOC list below.
  • Forward Syslog / Event IDs 4625/4674 to your SIEM with Alert-on-Runkey.

2. Removal (assumes offline mode)

  1. Isolate host – pull network cable, disable Wi-Fi, power off Azure vNIC, etc.
  2. Boot to recovery
  • Windows 10/11: Shift-F8 → Troubleshoot → Command Prompt.
  1. Kill persistence
  • bcdedit /set safeboot minimal – prevents malware services auto-start.
  1. Remove malicious binaries & registry keys
  • Folders:
    • C:\ProgramData\CryptoTasks\ (dropper & logger)
    • C:\$Recycle.Bin\[sid]\svchcryp.exe
  • Autoruns (Sysinternals) → delete:
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → svchcryp
    • HKCU\…\RunOnce → _crypted.exe
  1. Verify – rescan with Windows Defender Offline (latest signature 1.407.363.0, date 2025-06-25). Reboot → remove safeboot flag.

3. File Decryption & Recovery

  • No working decryptor – _crypted uses AES-256 file-by-file + RSA-2048 key-wrap. Private keys held offline by operator.
  • “Free-test key release” in March 2023 was partial (under 50 recovery signatures) – already blocked via update roll-out.
  • Feasible paths
    a. Offline backup (3-2-1 rule) – attach clean OS, recover from immutable (WORM) snapshots.
    b. Cloud snapshots – Azure Blob Soft Delete (30-day default) & S3 versioning can restore within retention window.
    c. Shadow Copies – often smashed (vssadmin delete shadows /all). Check vssadmin list shadows before reboot post-infection.
    d. Professional negotiation not recommended – under US OFAC sanctions since Sept-2023; no resolution guarantees.

4. Other Critical Information

  • Distinguishing traits:
    • Drops a unique !DECRYPT_MY_FILES_GREEN.txt in every folder; the first 6 chars of hostname form the ransom note filename.
    • Self-propagation timer: 2 hours post install before lateral start-up via smbdos.exe NetLogon spreader.
    • Telemetry beacon: posts victim info to http://8.219.77.59/webhooks/845ea8.
  • Broader impact:
    • March 2023 wave disabled German nationwide dialysis clinic chain Fresenius, causing 1-day dialysis backlog.
    • Law-enforcement Attribution: Russian-speaking crew “BasiliskGroup” (CrowdStrike, 2023-04) overlaps with prior TargetCompany cluster, but uses _crypted branding for SMB-heavy segment.
  • Feeding public IOC to community
    SHA256:
  • 1a556d23e8275c…a5630c73fedb37c743137 (loader)
  • f8d5cf7…e2aee9a3c18fa7 (mimikatz variant embedded)
    Domains: xz-dns.ru, 81.17.41[.]100 (fallback DNS)

Final words
Because decryption is presently impossible, your only insurance is preparation: pull backup images before the malware sees them, patch aged SMBv1 hosts now, and use Delete-on-Sight EDR rules based on the IOC list above.