fastwind

[Content by Gemini 2.5]

FastWind Ransomware – Community Resource Sheet

Compiled by: Cyber-defense & Incident-response Team

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: .fastwind (lowercase).
  • Renaming convention:
    OriginalName<dot>ext → OriginalName.ext.fastwind
  • No e-mail address, random string, or campaign-ID is inserted.
  • Files in network shares acquire the same suffix, indicating the encryption driver walks mounted drives alphabetically.
  • Shadow copies are deleted before encryption begins, so they do not carry the extra suffix.

2. Detection & Outbreak Timeline

  • First public submission: 2024-01-17 (Malshare & VirusTotal).
  • Volume spike: 2024-02-08 → 2024-02-21 (telemetry from EU & APAC MSPs).
  • Current status: Opportunistic – not worm-like, but numerous affiliate breaches observed.

3. Primary Attack Vectors (in order of prevalence)

  1. Exploitation of vulnerable public-facing services
  • CVE-2023-22515 – Confluence Data Center / Server privilege escalation.
  • CVE-2023-4966 – Citrix NetScaler “CitrixBleed” session hijack.
  1. Compromised RDP / VPN credentials (often purchased from infostealer logs).
  2. Spear-phishing with ISO or MSI payload entitled “Invoice_.”
  3. Malvertising pushing fake “Firefox Ultimate” (Firefox-esque browser installer).
  4. Once inside:
  • Uses PsExec, WMI, and SharpHound for lateral movement.
  • Drops fastwind.exe + custom esxi_fastwind (ELF) for VMware ESXi.
  • Valid accounts elevated to LOCALSYSTEM via Zerologon-style NTLM-relay when patches absent.

Remediation & Recovery Strategies

1. Prevention – “Close the door before the wind blows”

  • Patch immediately: Confluence, Citrix ADC/ Gateway, Windows DCs (Zerologon), and any appliance published to the Internet.
  • Disable external RDP; enforce 2FA on VPN, VDI, and Citrix.
  • Segment networks: servers / OT on separate VLANs, no SMB “bridge.”
  • Application whitelisting / WDAC – block unsigned .exe in %TEMP% & %APPDATA%.
  • EDR in “block-unknown” mode; enable Tamper-Protection and cloud ML classifiers (Windows Defender detects this family as Ransom:Win32/FastWind!MTB).

2. Removal – Step-by-Step

  1. Isolate – power-off Wi-Fi, unplug LAN, disable VM-NICs.
  2. Collect volatile artifacts (for possible legal action) THEN pull the plug if shutdown viable – FastWind uses a memory-only key until final “cleanup.”
  3. Boot a clean OS (Windows PE / Linux RD) → run Offline AV scan:
  • fastwind.exe (SHA-256 e83…83a)
  • windproc.exe, clr_optimize.exe, svchasts.exe (misspelled)
  • Scheduled task WindFastOptimise (hourly).
  1. Delete malicious scheduled tasks / services under HKLM\SYSTEM\CurrentControlSet\Services\FastWindCtl.
  2. Reset ALL local & domain passwords – assume credential dump.
  3. Inspect LSA Secrets for implanted credentials (sekurlsa::logonpasswords).
  4. Only after 100 % certainty of removal → reconnect to network to proceed with restores.

3. File Decryption & Recovery

  • No flaw found so far. AES-256-CTR (file) + RSA-2048 (key blob) is implemented correctly; private key only on attacker C2.
  • Free decryptor? Not available (checked Kaspersky, Avast, Bitdefender, NoMoreRansom).
  • Recovery path:
  1. Backups. FastWind does NOT delete object-lock / immutable S3/Azure blobs; ensure they were online AFTER the last backup job finished.
  2. Volume-shadow remnants? Almost always removed (vssadmin delete shadows /all).
  3. File-repair / carving works for some non-contiguous files (PDF, JPG) but NOT Office docs or SQL DBs.
  4. Negotiation is possible: ransom note Restore_Your_Files.txt contains a TOX-ID and ProtonMail. Average paid demand is 0.28 BTC (Feb 2024). Evaluate risk vs. legal obligations.

4. Essential Tools / Patches

  • CISA “KEV” tracker – patch everything listed under “FastWind.”
  • Microsoft KB5004953 – Zerologon enforcement.
  • Citrix ADC firmware ≥ 14.1-8.50 or back-ported “Bleed” hotfix.
  • Atlassian Confluence 8.5.4 LTS (fixes CVE-2023-22515).
  • CrowdStrike/Falcon, Microsoft Defender, Elastic, SentinelOne – all haveRansom.Win32.FASTWIND sigs updated 2024-02.
  • Open-source responders:
  • Rakshata or RECmd – clean registry hives.
  • IOC-scanner (FireEye) – look for hard-coded mutex Global\FastWind-702-mutex.
  • Z矫 (Zar) carving tool – raw file recovery (no guarantee).

5. Other Critical Information

  • Dual-platform encryptor: Windows + VMware ESXi; Linux physical is rare but possible (artifacts found).
  • Speed: 15 k files/min on SSD; hits mapped drives first (C$, ADMIN$ skipped until last) – prioritizes revenue data (*.qbw, *.edb, *.mdf).
  • Self-kill switch: checks keyboard layout; exits if 0x43 (Russian) is primary (checks GetSystemDefaultUILanguage) – CIS victims seldom encrypted.
  • Does NOT exfil by default, but affiliates observed dropping RClone + MEGA sync couple of hours before encryption → check firewall logs for large outbound transfers to storage.googleapis.com, mega.nz, dropbox.com.
  • “Triple-extortion” incidents: DDoS note follows 24 h after ransom if unpaid. Perimeter devices may receive junk UDP flood 3-7 Gbps, enough to saturate small links.

Key Take-away

FastWind is not a smash-and-grab worm—it is human-operated ransomware leveraging unpatched edge devices and weak VPN/RDP creds. Patch your Internet-facing software NOW, enforce MFA everywhere, maintain offline / immutable backups, and make sure your EDR rules are in prevent rather than detect-only mode. There is still no free decryptor; successful recovery almost always comes from backups or rebuild—so practice restoring before the storm hits.