fbsyw

[Content by Gemini 2.5]

Ransomware Resource Sheet

Variant tracked by encrypted-file extension: .fbsyw
(Community labels: “Fbsyw locker”, sometimes bundled with the Chaos / Onyx builder)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of file extension: Every encrypted file receives the suffix .fbsyw (lower-case).
  • Renaming convention: [original_name] + 4-to-6 random alphanumeric characters + .fbsyw
    Example: Quarterly.xlsx becomes Quarterly.xlsx_a9k4.fbsyw
    No fixed e-mail, TOR URL or victim-ID is normally written into the name, a trait typical of Chaos-derived strains.

2. Detection & Outbreak Timeline

  • First public submissions: 24 Jan 2022 (VirusTotal, ID-Ransomware).
  • Peak activity: March-May 2022 (cumulative >250 paid submissions to ID-R; dozens of English- and Spanish-language help-forum reports).
  • Occasional resurgence spikes: tied to cracked copies of the “Chaos 4.0 builder” surfacing on cyber-crime forums.

3. Primary Attack Vectors

  1. Malspam with double-extension .exe inside ISO or password-protected ZIP, themes: “Payment advise”, “DHL AWB correction”.
  2. Smash-and-grab RDP / compromised MSP credentials: attackers kill Defender, run fbsyw.exe from C:\Perflogs.
  3. Fake software installers (Photoshop, Office activators, pirated games) hosted on file-sharing sites; often bundled with adware dropper.
  4. No exploitation of OS-level 0-days observed to date; propagation inside LAN purely via network shares once an interactive beach-head is obtained.

Remediation & Recovery Strategies

1. Prevention

  • Disable RDP if not required; if required, use VPN-only access + GPO-enforced NLA, 2FA, and account lock-out.
  • Patch externally facing services (Citrix, Fortinet, Log4j, Exchange, etc.) – Fbsyw itself does not exploit them, but affiliates use the foothold.
  • E-mail gateways: strip ISO, IMG, and password-ZIP executables; use “double-keywords” rules for “invoice”, “payment”, “shipping correction”.
  • Application whitelisting / WDAC – block execution from %TEMP%, %PUBLIC%, C:\Perflogs, recycle-bin locations.
  • Back-ups that are OFFLINE (cloud with object-lock, or LTO with air-gap). Volume-shadow is deleted early by the malware—do NOT rely on it.

2. Removal (step-by-step)

  1. Physically disconnect network cable / disable Wi-Fi.
  2. Boot into Safe Mode with Networking or use a WinPE / Kaspersky Rescue / Bitdefender Rescue USB.
  3. Identify the offending binary: %Temp%\[4-6 random chars].exe, %Public%\Downloads\reboot.exe, C:\Perflogs\svhost.exe, or the user-run fake installer.
  4. Delete persistence:
  • Scheduled Task Updates\RebootTask (XML usually hidden in C:\Windows\System32\Tasks).
  • Run-key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\hostsv.
  1. Run a reputable, fully-updated AV (Defender, ESET, Kaspersky, Sophos) – all vendors have had signatures for “Ransom:Win32/Chaos!MSR”, “Trojan-Ransom.Chaos.a”, etc. since Feb 2022; this will clean the loader and secondary stealers.
  2. BEFORE re-joining the LAN, patch credentials (local admin and domain) – most breaches used admin:admin, Welcome123, company-name2021, etc.
  3. Re-image if business-critical system; otherwise keep the cleaned machine off production directories until backups are restored.

3. File Decryption & Recovery

  • Recovery feasibility: Currently UNLIKELY for versions seen to date.
  • Built on Chaos 4.x builder → hybrid XOR + random 32-byte key per file; private key never leaves memory or is sent to a C2 server.
  • There is NO free universal decryptor; Kaspersky, Emsisoft, NoMoreRansom list NO tool for .fbsyw.
  • Work-arounds:
  • Look for unencrypted copies: e-mail attachments, SharePoint recycle-bin, Teams cache, USB sticks, old laptops.
  • Professional data-recovery firms can sometimes salvage SQLite databases, mail PSTs and VM flat-files because the malware overwrites only the first 2 MB (Chaos limit) – success rate ≈30%; pay only on a “no-data / no-fee” basis.
  • Paying the ransom (0.04–0.08 BTC) provides a raw decryptor that often crashes on >2 GB files; negotiation lowers price ~30% but still no output guarantee → law-enforcement agencies DO NOT encourage payment.

4. Other Critical Information / Wider Impact

  • Differentiators:
  • Fast burn: encryption finished within 5-15 min; interrupts itself if Russian or Ukrainian keyboard layout is detected (coder left the Chaos geo-fence check).
  • Drops TWO ransom notes: read_it.txt on desktop + wallpaper replacement (BMP overlay).
  • Usually bundles RedLine or Azorult stealer – assume all credentials, browser cookies, crypto-wallets are compromised.
  • Broader impact:
  • SMB victims (<200 seats) dominated the Q1-Q2 2022 incident set; downtime ranged 1-14 days; average recovery cost (tech labour + new infra) USD 90k.
  • Report incident to local CERT / CISA / ICO / BfDI; Chaos variants have been used to create distraction while data-exfil occurs – verify logs for MEGASync.exe, rclone.exe, or PuTTY PSCP activity.
  • No evidence of hitting critical OT/ICS so far, but the highly automated builder is sold to many affiliates—expect the brand name “.fbsyw” to re-appear inside supply-chain attacks.

Stay safe—implement 3-2-1 backups, patch credentials, train users, and test the restore. With layered controls, even commodity Chaos-derived families like fbsyw become simply an inconvenience, not a business-ending event.