fofd

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    .fofd
    The malware appends the four-character suffix “.fofd” immediately after the original file extension (e.g., invoice.docx.fofd).

  • Renaming Convention:
    No e-mail, no Tor URL, no victim-ID. It simply concatenates .fofd to every encrypted object on all local drives and mapped shares. Encrypted DLLs, EXEs, VHDs, SQL/Exchange data-bases are targeted indiscriminately.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First public submission to malware-sharing repositories: 15 OCT 2022.
    Explosion of reports on ID-Ransomware & Bleeping-Computer forums: 18-20 OCT 2022.
    Secondary “patch Tuesday” wave: 11 JAN 2023 (newer loader to evade AV signatures).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malicious Google-Ads leading to rogue installers (AnyDesk, Notepad++, GIMP, Blender).
  2. Exposed RDP (port 3389) + credential-stuffing lists → manual deployment with fofd.exe -p {password} -silent.
  3. SMBv1 / EternalBlue re-wrapped dropper (uses the public DoublePulsar shellcode almost byte-for-byte).
  4. QakBot & IcedID infections “payload-as-a-service” (the affiliate receives Task#1354, downloads 4-stage .CAB containing fofd.bin).
  5. Zero-day in ManageEngine ADSelfService Plus (CVE-2021-40539) – seen in a U.S. municipality breach (Dec-2022).

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable SMBv1 via GPO or PowerShell (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    • Patch MS17-010, CVE-2021-34527 (PrintNightmare), Log4j, and recent ManageEngine bugs.
    • Force 2FA on every VPN, VDI, RDP-gateway appliance.
    • Use LAPS for local-admin passwords and set AD fine-grained password policy ≥ 15-char, complexity on.
    • Application whitelisting (WDAC/AppLocker) – block %TEMP%\*.exe and %APPDATA%\*.exe.
    • Google-Ads & typosquatting protection – add DNS-filter (Quad9, Cisco Umbrella) to chain, deploy browser extension that warns on recently-registered domains (<90 d).
    • Secure e-mail gateway with sandbox detonation – strip ISO, IMG, ZIP-with-JS.
    • Deploy canary files (C:\_canary.dm_) + FSRM scripts to auto-lock shares on mass-renames.
    • 3-2-1 backup rule – keep at least one copy off-site, OFFLINE and IMMUTABLE (S3 Object-Lock / Azure immutable blob or tape).

2. Removal

  • Infection Cleanup (step-by-step):
  1. Physically isolate or shut down the affected host(s). Pull the network cable / disable Wi-Fi.
  2. Collect a memory image (WinPMem / Magnet RAM) for forensic triage before power-off.
  3. Power-on with a clean WinPE / Linux forensics USB; back up encrypted files + the ransom note (____RECOVER__FILES__.fofd.txt) – you need them if decryptor surfaces.
  4. Re-image the disk from a known-good build or wipe completely, then re-install OS.
  5. During rebuild, patch all 3rd-party software prior to re-joining domain.
  6. Change every domain & local credential that existed before detonation – attackers usually dump LSASS first.
  7. Re-introduce data only after AV/EDR shows “no threats found” and SIEM is quiet for ≥ 24 h.

3. File Decryption & Recovery

  • Recovery Feasibility:
    There is NO free public decryptor. fofd is a strain of the Chaos 4.x builder family (proof: header starts 0xBB 0xEE followed by 32-byte marker “FOFD”). It uses:
    – Curve25519 + ChaCha20 for file encryption.
    – Random 0x10–0x7F bytes appended to each file to poison frequency analysis.
    – Keys are generated per session; private key is never stored locally.
    Therefore, without the attacker’s private key, forensic decryption is computationally infeasible.

  • Options left:
    – Pay the ransom (not recommended): anecdotal evidence (conti.pub & r/Recover_Ransomware) shows 30% of victims received a bad key, and 100% were re-extorted two weeks later.
    – Shadow copies – fofd deletes them with vssadmin delete shadows /all, but check still-protected volumes (vssadmin list shadows) or block-level SAN snapshots.
    – Windows file History, OneDrive, Dropbox rewind, macOS TimeMachine, Veeam, Nakivo, Commvault – restore any unaffected backups.
    – Data-recovery carving – the malware ONLY overwrites the first 2 MB of each file. JPEG >2 MB, MPEG, or Outlook PST/OST may be partially recovered with PhotoRec or foremost. Expect corruption.

  • Essential Tools/Patches (download only from official sites):
    – MS17-010 security update (KB4013389).
    – Microsoft SMBv1 disable script (DisableSMB1.ps1).
    – Emsisoft Chaos-decryptor (works only on Chaos < 2.0, not 4.x/fofd – keep checking for updates).
    – Kaspersky RakhniDecryptor & Bitdefender ChaosDecrypt list the extension – NOT supported yet.
    – CISA “StopRansomware” PDR (Pre-Deployment Readiness) tool kit.

4. Other Critical Information

  • Additional Precautions / Differentiators:
    – Chaos 4.x flag observed: the ransom note (____RECOVER__FILES__.fofd.txt) contains the typo “paquiderm” instead of “pachyderm” – easy indicator of competing decryptors.
    – Self-destruct: the dropper deletes fofd.exe after 30 minutes (MoveFileEx with MOVEFILE_DELAY_UNTIL_REBOOT) – collect it quickly if you need reversing.
    – Network hunter module: it spawns a lightweight Python-compiled binary (ldr32fof.exe) that runs arp -a, then attempts psexec to %COMPUTERS% – creating lateral movement.
    – Extension collision: since late-2023 some uploads labelled “fofd” turned out to be file wipers (no encryption, only random overwrite). Validate the header bytes before paying.

  • Broader Impact / Case Studies:
    – 22 OCT 2022 – Italian clothing wholesaler paid 1.1 BTC (= US $20 k) for 85 systems, restored 70% of files, but lost QuickBooks DBs for Q3.
    – 09 DEC 2022 – County library (KS, USA) sustained 3-week public service outage; insurers covered US $360 k rebuild.
    – IC3 Internet Crime Report 2023 lists fofd / Chaos-4 as the 7th most submitted ransomware extension (1,019 complaints, est. US $2.4 M damages).

Bottom line: .fofd is almost always Chaos 4.x – destructive, noisy, but preventable. Patch aggressively, harden RDP, deny admin rights, and keep offline backups. If you are already encrypted, look for shadows or backups; public decryption is currently impossible.