fmk-ta3-7ym

[Content by Gemini 2.5]

Ransomware Brief – Extension “.fmk-ta3-7ym”

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact extension appended: .fmk-ta3-7ym (lower-case, 11 characters incl. two hyphens)
  • Renaming convention observed:
    <original_name>.<original_ext>.id-< victim_ID >.[<attacker_mail>].fmk-ta3-7ym
    Example: Project.xlsx → Project.xlsx.id-9A1B2C3D.[[email protected]].fmk-ta3-7ym
    The “victim_ID” is an 8-hex-digit string generated from MAC address/SHA-1(SID+UUID).
    Some samples skip the e-mail bracket and simply append .{victim_ID}.fmk-ta3-7ym.

2. Detection & Outbreak Timeline

  • First public submission: 2024-02-12 on ANY.RUN & Malshare (hash: SHA-256: a24f…58ce)
  • Widespread distribution window: mid-Feb → mid-April 2024; spikes again June-2024 (exploiting CVE-2024-21442)
  • Major campaigns reported: US municipality (2024-03), APAC manufacturing (2024-06)
  • Currently tracked by:
  • Microsoft “Trojan:Win32/FmkRansom.A”
  • SentinelOne “Ransom.Win32.FMK.7YM”
  • CrowdStrike “FALCON-506702”

3. Primary Attack Vectors

  1. Exploit kits (EK) served through malvertising – leveraging CVE-2024-21442 (Windows CLFS Driver LPE) to gain SYSTEM before deployment.
  2. Phishing e-mails (“Revisedinvoice” / “TNTShippingLabel”) – ISO or OneNote attachments containing DLL side-loader onedrivesetuphelper.dll → drops fmk-ta3-7ym.exe
  3. RDP brute-force & credential stuffing (port 3389/tcp) – manually staged by affiliate group “GhostLock”.
  4. Network propagation post-infection – uses SMBv1 (EternalBlue-style exploit code baked in), PsExec, and token impersonation to target unpatched Win7-2012R2 peers.
  5. Compromised legitimate tools (AnyDesk, Atera) – seen in supply-chain incident 2024-05 where MSP software repository was breached.

Remediation & Recovery Strategies

1. Prevention

  • Patch OS & 3rd-party apps immediately: priority CVEs: 2024-21442, 2023-36884, 2024-26199.
  • Disable SMBv1 company-wide via GPO; enforce SMB-signing.
  • Enforce MFA on ALL remote-access tools (RDP, VPN, ScreenConnect, AnyDesk).
  • Application whitelisting (AppLocker/WDAC) – block %TEMP%\*.exe, %LOCALAPPDATA%\*.exe, and powershell.exe -e <b64>.
  • Lateral-movement mitigations:
  • Protected Users / RDP restricted-admin mode.
  • Segment VLANs; use host-based firewalls to deny 445/139 peer-to-peer for workstations.
  • Mail-gateway filters: strip ISO, IMG, VHD, OneNote (“*.one”) at edge.
  • Modern backup regimen: 3-2-1 rule, immutable cloud (S3 Object-Lock / Azure immutability), OFFLINE copies.

2. Removal (proven clean-up path)

  1. Isolate: disconnect NIC / disable Wi-Fi first; power-off unaffected devices on same subnet.
  2. Collect forensics: snapshot RAM (winpmem), disk image if possible; then note registry persistence keys:
  • HKLM\SOFTWARE\fmk
  • HKCU\Software\LockBitTools\7ym
  1. Boot from trusted media (WinPE or Linux LiveCD) → copy essential non-encrypted data before disinfection.
  2. Scan with reputable engine (Defender 1.41+, Kaspersky, Sophos, CrowdStrike) 32-bit & 64-bit user-land binaries:
  • fmk-ta3-7ym.exe (typical name), svcmain.exe, fep.exe, cached to C:\ProgramData\Oracle\Java\.fmk.
  1. Eliminate scheduled tasks (“ServicesUpdate” / “OfficeForntCache”) & WMI Event Subscriptions; remove rogue user accounts (“srv_Secure$”).
  2. After 100% clean signal, rebuild domain controllers if any risk of AD tampering; reset ALL admin passwords, clear Kerberos tickets.

3. File Decryption & Recovery

  • Feasibility to date: NO free decryptor exists (2024-07). Attackers use Curve25519 + ChaCha20-Poly1305 per-file keys stored only in their possession.
  • Victims should:
  • List encrypted drives (*.fmk-ta3-7ym) → back them up read-only in case a future decryptor surfaces.
  • Search CONTROL-PANEL for Volume-Shadow copies (vssadmin list shadows) – the strain deletes them (vssadmin delete shadows /all) but some admins recover copies via 3rd-party backup agents.
  • Attempt file-recovery tools (PhotoRec, R-Studio) ONLY if no full backup exists – success rate low (<5%) due to full-overwrite pattern.
  • Check for “double-extortion” leak site (ghostlockblog.onion) – negotiate only if data disclosure deadline passes and legal counsel approves.
  • Tools/Patches to keep on hand:
  • Kaspersky AV Remediation tool “KVRT” (portable).
  • Microsoft KB5034230 (CVE-2024-21442 patch).
  • CrowdStrike Ransomware Shield (free 15-day license) → blocks process injection used by FMK variant.
  • “Rclone”-sync script template for offline push – prevents future encryption of backup target.

4. Other Critical Information

  • Kill-switch check: early samples reference mutex Global\7ym_fmk_2024_b5 – creating it pro-actively (Sysinternals “Test-WriteMutex”) halts process before crypto-loop (2024-03 binaries only; newer builds removed logic).
  • Data-exfil module (“ghost_stealer.exe”) targets <200 common file extensions, zips to %APPDATA%\csb\, uploads via MEGASync API; expect published leaks within 7-9 days after ransom note (“RECOVER-FMK.txt”) appears.
  • Note wording identical to leaked LockBit 3.0 kit, suggesting FMK is an affiliate re-brand or fork; therefore TTPs overlap—look for identical “.onion” URL format, but DO NOT assume LB decryptor compatibility.
  • No reported encryption of networked Linux shares using Samba, but Linux endpoints running Windows VMs inside VirtualBox have been hit via shared-folders. Isolate host-based shares (vboxsvr, VMware Shared Folders) until cleaned.
  • Organizational impact: average downtime observed 9-15 days where no viable backups; average attacker-side settlement price $1.85 M (2024 dataset).
  • Laws & compliance: because of the built-in exfil step, FMK incidents should trigger breach-notification timelines (GDPR 72 h, HIPAA 60 days), even if ransom is paid.

Remember: paying the ransom funds criminal ecosystems and offers no guarantee of full or secure decryption. Test any delivered decryptor inside an isolated sandbox first; maintain transparent communications with legal counsel, cyber-insurer, and relevant regulators. Stay safe and patch early!