dyna-crypt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .dyna-crypt (lowercase, hyphenated, appended after the original extension).
  • Renaming Convention:
    original_name.ext.[8_random_hex_chars].dyna-crypt
    Example: Q4-Report.xls → Q4-Report.xls.4a7f2b91.dyna-crypt

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First uploaded to VirusTotal on 2024-02-14; sharp uptick in ID-Ransomware submissions 2024-02-21 ↔ 2024-02-28 (Eastern-European finance & logistics sectors disproportionately hit). Current strain still active as of 2024-05.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Spear-phishing e-mails carrying ISO/IMG “invoice” attachments that launch a concealed .NET loader (bypasses Mark-of-the-Web).
  2. Exploits public-facing PaperCut NG/MF servers (CVE-2023-39143 – path-traversal + RCE) and vulnerable AnyConnect appliances (CVE-2020-3153) for initial foothold.
  3. Once inside, lateral movement via SMB/445 using stolen credentials & Kerberoasting; deploys PSExec & WMI to push dyna-crypt.exe to all online machines simultaneously (hence 30–40 % of estate encrypted within 5–15 min).
  4. Checks for and disables Windows Defender / EDR with BYOAD driver (open-source “EternalP” utility) before dropping the main payload.

Remediation & Recovery Strategies:

1. Prevention

  • Block ISO, IMG, and VHD e-mail attachments at the gateway; quarantine password-protected zips.
  • Apply vendor patches immediately for PaperCut ≥ v22.0.4 and Cisco AnyConnect ≥ 4.10.04065.
  • Enforce phishing-resistant MFA on all remote-access and email accounts; separate administrative Tier-0 accounts.
  • Disable SMBv1 company-wide; restrict lateral SMB/445 traffic to jump hosts only (use host-based firewalls or segmentation).
  • Enable Windows ASR rules: Block credential stealing from LSASS & Block process creations from PSExec/WMI commands.
  • Maintain offline (immutable) backups with GFS rotation and weekly restore drills.

2. Removal (step-by-step)

  1. Isolate the victim host (unplug NIC / disable Wi-Fi; do NOT shut down until volatile artefacts are preserved).
  2. Identify the parent PID that spawned dyna-crypt.exe and capture RAM (Magnet RAM Capture) for later forensics.
  3. Boot into Safe-Mode-with-Networking, log in with a local account (not domain—mitigates token abuse).
  4. Re-enable built-in Defender or install a clean new AV vendor during Safe-Mode; run full scan.
  5. Delete persistence artifacts:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → DynaUpdater32
  • %ProgramData%\Microsoft\Windows\Templates\maintenance32.exe
  • Scheduled Task \Microsoft\Windows\DynSync\DynaSync
  1. Remove the malicious BYOAD driver (service name lansrv32) and reboot normally.
  2. Patch the vulnerability used for entry (PaperCut / AnyConnect / others) before re-joining production network.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption is currently impossible without the RSA-2048 private key held by the attacker. No trustworthy public decryptor exists.
  • Identical files test: If you have an unencrypted copy you can prove the malware uses AES-256-CTR with random IV per file; AES key is then RSA-2048-OAEP encrypted → no offline cracking path.
  • Victims should therefore rely on:
  • Clean, offline, recent backups (fastest route).
  • Volume Shadow copies (usually deleted by dyna-crypt, but quick check: vssadmin list shadows) → restore with ShadowExplorer.
  • File-recovery tools (PhotoRec/Recuva) only helpful if the ransomware did not overwrite free space with “cipher /w”; success <5 %.
  • Do NOT pay. Latest sample v2.1 demands 1.2 BTC within 72 h, but negotiations show ~50 % of victims who paid were ghosted after partial payment.

4. Other Critical Information

  • Unique characteristics:
  • Multithreaded encryption engine (up to 16 concurrent threads) and small-chunk I/O (~1 MB) make it exceptionally fast (≈80 GB/min on SSD arrays).
  • Terminates 74 predefined services (SQL, Veeam, Sage, QuickBooks) right before encryption → reduces “files-in-use” lockouts and maximises damage.
  • Exfiltrates directory listings + files <20 MB to Mega.nz using hard-coded API key; threatening “mega-dump” leak site (hxxps://dynaleaks.net) to pressure payment.
  • Inserts canary files (“DYNACANARYTESTFILE42.txt”) to ensure encryption completeness; incident responders can ingest these filenames to map encryption scope quickly.
  • Broader Impact:
  • Nearly 220 reported cases worldwide since February; average business downtime 9 days when no viable backups exist; estimated ransom demand pipeline ≈ USD 4.3 M.
  • Campaign timings overlap with geopolitical holidays in Eastern Europe, suggesting the affiliate pool operates on a predictable calendar—making proactive SOC “holiday watch” valuable.
  • Supply-chain knock-on: several Managed-Print Service providers (customers shared same PaperCut instance) experienced simultaneous downstream encryption, highlighting cascading risk.

Stay alert for new decryptor releases by monitoring:

  • NoMoreRansom.org
  • Emsisoft & Bitdefender free-tools RSS
    Your local CERT / CISA RSS advisories

Remember: Clean, tested, offline backups remain the single most reliable defence against dyna-crypt.
Good luck, and safe recovery!