filesfucked

[Content by Gemini 2.5]

TECHNICAL BREAKDOWN:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .filesfucked (lowercase) is appended to every encrypted file.
  • Renaming Convention: Original-name → <original_name>.<original_ext>.filesfucked.
    Example: 2024-Q3-Budget.xlsx becomes 2024-Q3-Budget.xlsx.filesfucked.
    The ransomware does NOT change the base filename, which is useful when rebuilding from backups/logs.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public submission to VirusTotal 21-Jul-2023; active clusters reported on English-language tech-help forums throughout Aug-2023. Peak distribution window: 20 Jul – 30 Sep 2023, with sporadic re-appearance in Q1-2024.

3. Primary Attack Vectors

  • A. Phishing e-mail with ISO/IMG lure – message claims to be “Docusign invoice”; ISO contains a .NET dropper (MsBuild.exe masquerade) that side-loads the 32-bit encryptor DLL.
  • B. Smaller subset via RDP brute-force – attackers use NLBrute/TSG then manually execute filesfucked.exe once Domain-Admin is achieved.
  • C. Pirated-software channels – fake Adobe & AutoCAD “cracks” seed the same .NET dropper.
  • No evidence of worm-like SMB exploit (NOT leveraging EternalBlue, Log4Shell, etc.). Once inside, lateral movement is manual: PowerShell, PSExec and RDP.

REMEDIATION & RECOVERY STRATEGIES:

1. Prevention

1.1 Strip/Block e-mail attachments: ISO, IMG, VHD, DLL inside ZIP.
1.2 Disable / restrict inbound RDP (TCP-3389) from the Internet; enforce lock-out policy after 3–5 failed logins; use VPN with MFA instead.
1.3 For local admin: LAPS + tiered accounts; no shared local passwords.
1.4 Application whitelisting (Windows AppLocker or WDAC) – block execution of unsigned binaries inside %TEMP%, %PUBLIC%, C:\PerfLogs.
1.5 Keep full offline plus immutable cloud backups (object-lock / S3 Versioning / Azure immutable blob). Follow 3-2-1 rule and perform quarterly restore tests.

2. Removal

Power down affected asset; boot from a clean USB running WinPE/Live-Linux:
a. Manually delete:
%TEMP%\rel<random>.dll,
C:\Users\Public\Libraries\dllhost.exe,
Run registry key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\dllhost = "C:\Users\Public\Libraries\dllhost.exe"
b. Clean Task Scheduler entries named OnceTask, UpdaterAC.
c. Run a reputable offline AV/EDR scanner to mop-up remnants (Defender Offline, Kaspersky Rescue, Bitdefender BR, Malwarebytes PE).
d. Verify lateral foothold is gone on all peer machines before bringing anything back on-line.

3. File Decryption & Recovery

There is currently NO working decryptor. Filesfucked is a simplified offshoot of “Chaos 4.0 builder”:

  • Drops 2-byte marker 0xF4 0x5C at EOF – random ecosystem cliché, not cryptographic weakness.
  • Uses per-file random 32-byte key → RSA-1024 public key embedded in binary. Without the attacker’s private key, brute-forcing the 1024-bit modulus is computationally infeasible.

Recovery path:

  • Restore from immutable/offline backup.
  • Linux-based file-carving (PhotoRec) will give you partially intact plain-copy material ONLY if the ransomware was interrupted.
  • Shadow-copy usually wiped (vssadmin delete shadows), but an OFT-uncleaned backup job may contain intact .vhdx; check backup appliances before formatting.
  • Engage your cyber-insurer/incident-response retainer; negotiation is possible—some affiliates accept 0.06 BTC ($1.8 k), but payment still carries no assurance.

4. Other Critical Information

  • Families derived from Chaos builder (including Filesfucked) randomly corrupt files >2 MB ≈ 15% of the time; therefore decrypted/hijacked binaries must be validated.
  • No built-in data-exfil module seen so far; threat actor sometimes stages data manually post-exploit (credential dumps, ProductPriceList.xlsx, etc.). Assume leak exposure even though ransom note does not mention it.
  • When the ransom note READMETORESTORE.txt appears, it often copies itself to every folder and later sets the wallpaper; deleting the note does not harm decryptability, so you may purge it during cleanup.

If you choose to rebuild rather than negotiate: Wipe the system drive fully (including EFI/MSR) before re-imaging; Chaos variants have been seen to “hibernate” in ESP partition and reinfect during the next reboot.

Stay safe, patch people before patching machines, and keep backups logically separated from production—your fastest path to “Files-FIXED” against Filesfucked.