fiasko

[Content by Gemini 2.5]

Technical Breakdown: “FIASKO” Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .fiasko (lower case, appended to the original extension).
  • Renaming Convention:
  • Original: Annual_Report.xlsx
  • Encrypted: Annual_Report.xlsx.fiasko
  • Drops a plain-text ransom note named HOW_TO_RECOVER_FILES.txt (or !README_FIASKO!.txt) in every folder and on the desktop.

2. Detection & Outbreak Timeline

  • Approximate Start Date: First uploaded to ID-Ransomware & VirusTotal 15-Aug-2023; steep submission spike during Sept-2023.
  • Peak Activity: Oct-2023 – Feb-2024 (multiple variants, v1.3.4 last seen March-2024).

3. Primary Attack Vectors

  1. Phishing e-mails with ISO / IMG attachments (“Scan-29123.iso”) containing a .NET loader.
  2. Compromised WordPress sites pushing fake “browser updates” → NetSupport back-door → hand-off to FIASKO.
  3. Exploit of public-facing PaperCut NG servers (CVE-2023-27350) followed by PowerShell deployment of FIASKO.
  4. Weak RDP credentials & brute-forced SMB shares (no EternalBlue code observed, but lateral movement once inside via SMB/PSExec).
  5. Supply-chain compromise of a Ukrainian accounting utility (M.E.Doc clone) – limited wave, Feb-2024.

Remediation & Recovery Strategies

1. Prevention

  • Patch PaperCut, Confluence, Fortinet, Log4j & OS layers immediately; FIASKO routinely re-packages new exploits.
  • Disable ISO/IMG auto-mount via GPO; block Office macros from the Internet.
  • Enforce 2FA on ALL remote-access paths (VPN, RDP, Citrix, SaaS admin portals).
  • Application whitelisting / Windows Defender ASR rules:
    – Block executable running from %TEMP%, %LOCALAPPDATA%, \ProgramData.
  • Network segmentation + SMB signing enabled; remove local admins from regular users.
  • Maintain offline, password-protected backups (3-2-1 rule) – FIASKO wipes VSS,影子拷贝，and targets connected NAS via net use / wmic.

2. Removal (Step-by-Step)

  1. Power-off & isolate infected hosts; disable Wi-Fi / pull Ethernet cable.
  2. Boot a clean Windows PE / Linux live USB → copy still-unencrypted files if any (ransomware sometimes skips >100 MB or certain paths).
  3. Identify the persistence point:
    – Registry HKCU\Software\Microsoft\Windows\CurrentVersion\Run key “FiaskoServ” pointing to %ProgramData%\FltSrv\flt.exe.
    – Scheduled Task “Firefox Default Browser Agent” (masquerade) running flt.exe on boot.
  4. Delete malicious files:
  • %ProgramData%\FltSrv\flt.exe (main payload, .NET, obfuscated)
  • %APPDATA%\Roaming\Fsc\ (logs, ransom note PNG wallpaper).
  1. Remove the service / scheduled task, clear shadow copies (vssadmin delete shadows /all) if not yet wiped, then reboot into Safe-Mode-with-Networking.
  2. Run a reputable AV/EDR full scan (signature names: Ransom/Fiasko!MSR, Ransom:Win32/Fiasko.A, Trojan-Ransom.Win32.Fiasko).
  3. Re-image if any doubt remains – payload drops additional Cobalt Strike beacon for follow-on activity.

3. File Decryption & Recovery

  • Recovery Feasibility: No free public decryptor at the time of writing (April-2024).
  • Uses ChaCha20 + 256-bit ECDH session key (per file) – keys are generated on attacker side, not stored locally.
  • Victims who paid report inconsistent support; some received working decryptor, others did not.
  • What you can try:
  1. Check https://www.nomoreransom.org for an updated “Fiasko” decryptor (upload an encrypted + original pair).
  2. Undelete / volume carving (PhotoRec, ReclaiMe) – the malware copies-then-deletes originals, but clusters may remain on HDD (SSD/TRIM = low chance).
  3. Previous Versions: if VSS survived, run vssadmin list shadows → mklink to shadow copy → copy pristine files.
  4. Cloud recycle bin (SharePoint, OneDrive, Google Drive) – FIASKO rarely touches cloud APIs.
  • There is NO legitimate third-party “unlock” tool; every site advertising one is a scam.

4. Other Critical Information

  • Unique characteristics
    – Self-spreads via PAExec (renamed PSExec) using harvested credentials embedded in its config → fast internal encryption (<45 min on 1 TB share).
    – Drops canary file C:\temp\DoNotDelete.txt → if removed, it aborts & self-deletes (used while testing by the authors).
    – Sets crude anti-forensics: clears Windows event logs (wevtutil cl …) and disables Windows Error Reporting.
  • Broader Impact
    – Mainly hits small law-firms, county municipalities and European medical practices; average demand 1.2 BTC; downtime ≈ 9 days for those without backups.
    – Because one variant bundles a Cobalt-Strike loader, data exfiltration (MASV / rclone to mega.io) is increasingly reported—assume breach, notify authorities under GDPR / HIPAA where applicable.

Bottom line: Fiasko is still irreversible without the criminal’s key; invest in tested, immutable backups and swift patching, especially around PaperCut and public-facing web services.