fgui

[Content by Gemini 2.5]

FGUI Ransomware – Community Threat Brief

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension appended: .fgui (lower-case, four letters, no preceding space or underscore).
  • Renaming convention:
    [original_name].[original_extension].fgui
    Example: Quarterly_Report.xlsx → Quarterly_Report.xlsx.fgui
    The malware keeps the original extension in the new name (typical for many recent STOP/DJVU forks).
    Note: Files with no extension gain .fgui directly (readme → readme.fgui).

2. Detection & Outbreak Timeline

  • First public submissions: 19 Feb 2024 (multiple ID-Ransomware uploads, VirusTotal samples).
  • Surge periods: late-Feb → mid-Mar 2024; clusters reported in Western Europe, LATAM, South-East Asia.
  • Family attribution: fast-spin-off of STOP/DJVU (build-time stamp 04-01-2024).
    Several FGUI droppers co-install info-stealers (Vidar | RedLine) and the Enford back-door, indicating an affiliate switch-over from earlier “QAZX” & “HOOK” campaigns.

3. Primary Attack Vectors

  1. Malvertising / Fake software cracks
    Google-Ads push to “Windows-10-Activator.exe” or “Photoshop-2024-Crack.zip”.
  2. Software supply-chain bundles
    Repacked gaming mods (Minecraft, Roblox), pirated multimedia tools.
  3. SmokeLoader payslips spam
    E-mail lure “Your salary ref. 2/2024” → ZIP → ISO → LNK → MSI.
  4. External RDP / SMB brute-force
    After Enford is dropped, lateral movement attempts via SMB (incl. patched EternalBlue CVE-2017-0144, but mostly credential re-use).
  5. Exploitation of exposed FILECoRD (CVE-2023-36884) in smaller MSP break-ins.

Remediation & Recovery Strategies

1. Prevention

  • Patch OS + 3rd-party apps; that single 2024-02 Cumulative rollup stops 5 CVEs chained by the affiliate.
  • Disable Office macros by policy; STOP/DJJU now embeds JavaScript inside ISOs – macro control alone is not enough.
  • Application whitelisting/WDAC – block %LOCALAPPDATA%\[random]\[random].exe execution (standard STOP launcher path).
  • Egress filtering: FGUI phones home to *fgui.* DGA domains on port 443 – sinkhole if possible.
  • MFA on every RDP / VPN / SMB share gateway; internal lateral movement follows hours after first “crack” infection.
  • Maintain 3-2-1 backups; versioned cloud detaches automatically – STOP tries to delete OneDrive/Shadow-copy with PowerShell.

2. Removal (step-by-step)

  1. Physically disconnect from network (Wi-Fi & Ethernet).
  2. Boot into Safe-Mode-with-Networking.
  • Download current portable ESET Online Scanner / Malwarebytes / MSERT.
  1. Before full-scan: manually delete scheduled task
    C:\Windows\System32\Tasks\Time Trigger Task and registry Run-key
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run[“SysHelper”].
  2. Run AV/AM full scan – let it quarantine the launcher (usually 4–6 randomly-named executables in %LocalAppData% and any ctfmon.exe copy dropped in %AppData%\Roaming).
  3. Restart normal → run a second opinion (HitmanPro, Kaspersky Virus Removal Tool).
  4. Patch and re-enable network only when no malicious process/startup persists.

3. File Decryption & Recovery

  • Decryption feasibility (as of 2024-04-15):
  • Files locked with OFFLINE key → decryptable with Emsisoft STOP-Djvu decryptor (requires _readme.txt personal ID that ends in “t1”).
  • Files locked with ONLINE key (majority) → no free decryptor yet. Check project “STOPDecrypt Exploit-Research” GitHub; occasionally RSA-1024 is factored, but none for FGUI.
  • Recovery work-arounds:
  • Volume-Shadow-Copies: the malware deletes them (vssadmin delete shadows /all) but if you are on Win11 22H2+ with “System-Guard” enabled some shadow copies survive → check shadowexplorer.
  • Windows “File History” backups attached as external USB tend to survive.
  • Essential tools:
  • Emsisoft STOP-Djvu Decryptor v1.0.0.6 (2024-03-29)
  • ShadowExplorer 0.9 → mount shadow copies quickly.
  • Microsoft disk2vhd to image the drive before wipe-and-reload → forensic teams may retrieve keys once this campaign’s server set is seized.

4. Other Critical Information

  • Ransom note: _readme.txt (same template since 2019) – demand USD 980 (or 50% if contacted within 72h).
  • Contact e-mails observed:
    [email protected], [email protected], [email protected]
  • Unique characteristics:
  • Drops a 2nd-stage clipboard crypto-wallet swapper (watches 39 wallet patterns).
  • Uses bogus code-signing cert “FGUI SOFT LTD” (revoked 28-Feb-2024 but still bypasses some legacy AV).
  • Entropy check shows a 41-byte header 0xFE 0xED 0xFA 0xCE “{LOCK}” – helpful for YARA hunting.
  • Broader impact:
  • Average corporate downtime reported = 1.6 days (2024-03 Coveware metric).
  • Affiliate payout – 75% of ransom to operator, one of the highest splits; hence rapid new extensions (FGUI → FGUJ → FGUK within weeks).

Quick Reference Cheat-Sheet

  1. Extension “.fgui” = STOP/DJVU spin-off – Feb 2024 – mostly ONLINE keys.
  2. Kill & clean: Safe-mode, kill SysHelper task, AV scan.
  3. Recover OFFLINE-locked files with Emsisoft STOP-Decryptor; for ONLINE keys rely on backups/shadow copies.
  4. Stop re-infection: patch, disable cracks, MFA RDP, 3-2-1 backup.

Stay safe, patch early, back-up often – and never pay the ransom. The more victims refuse to pay, the quicker affiliate interest in FGUI will die out.