flatcher3

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .flatcher3
  • Renaming Convention: Appends “.flacher3” to every encrypted file (e.g.,
    Quarterly_Report.xlsx → Quarterly_Report.xlsx.flatcher3).
    Inside each folder a plain-text ransom note named HOW_TO_RETURN_FILES.txt is dropped; no desktop wallpaper change or registry-based note has been observed.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First submitted to public malware repositories on 2024-01-17, with telemetry clusters peaking between 24-Jan and 02-Feb-2024 in Europe and LATAM.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mails with ISO/IMG (“FedEx invoice”, “DHL package”) attachments.
  2. Malvertising leading to Fake-Updates (Chrome / Edge patch) that drop an NSIS installer (ChromeSetup.exe).
  3. External RDP brute-force followed by manual deployment of flatcher3.exe from C:\PerfLogs\.
  4. Exploits for vulnerable Atlassian Confluence (CVE-2023-22515) and Citrix NetScaler (CVE-2023-4966) observed in at least three incident-response cases.

Remediation & Recovery Strategies:

1. Prevention

  • Patch Confluence, Citrix, Exchange and Windows (especially SMB) aggressively.
  • Enforce phishing-resistant MFA on all VPN / RDP / remote-admin gateways.
  • Disable Office macros by GPO; block ISO/IMG at the mail gateway unless whitelisted.
  • Maintain offline, immutable backups (3-2-1 rule) and test a bare-metal restore quarterly.

2. Removal

  1. Disconnect from network (pull cable / disable Wi-Fi) immediately.
  2. Boot into Safe Mode with Networking or a reputable WinPE recovery stick.
  3. Locate and kill the launched copy:
  • Common paths: %TEMP%\[random]\flatcher3.exe, C:\Users\Public\Libraries\flatcher3.exe, C:\PerfLogs\.
  1. Delete persistence entries:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SystemSound,
  • Scheduled task \Microsoft\Windows\Multimedia\SystemSoundService.
  1. Run a full scan with updated AV / EDR; the sample is detected generically as:
    Ransom:Win32/Flatcher.A, Trojan-Ransom.Win32.Gen.fl, RansomX-gen.
  2. Before re-joining the network, patch the entry vector (reset breached account, change RDP port, add IP whitelist, install Confluence/Citrix hot-fix).

3. File Decryption & Recovery

  • Recovery Feasibility: Files are encrypted with ChaCha20 + RSA-2048 (unique key per victim). No implementation flaw or leaked master key exists at the time of writing (2024-May). Free decryption is therefore impossible.
  • Restoration Only Possible Via:
  1. Clean, offline backups;
  2. Volume-Shadow copies (only if the malware failed to delete them – check vssadmin list shadows before cleanup);
  3. Third-party rollback tech (e.g., Windows Server“Previous Versions”, EDR-provided file-recovery cache, certain NAS snapshots).
  • Essential Tools/Patches:
    – Confluence 8.5.4 or 8.7.3+, NetScaler 14.1-8.50+, MS patches for SMB, MS Office “Block macros from internet” policy.
    – SentinelOne, CrowdStrike, Sophos and Microsoft Defender platform updates released between Jan-24 and Mar-24 add behaviour-based coverage for Flatcher3.

4. Other Critical Information

  • Additional Precautions:
    – The malware self-terminates on systems with Russian or Belarusian UI languages; still treat those machines as compromised because lateral movement may already have occurred.
    – Uses WMIC shadowcopy delete and bcdedit /set {default} recoveryenabled No to hamper recovery; logging those commands in Windows Event IDs 1 & 4104 is an early indicator.
  • Broader Impact: Early incidents forced a 4-day shutdown of production lines at a European food manufacturer and a week-long outage at a Colombian health network (EMR unavailable). Expect operators to auction “proof” packs on dark-web forums rather than operate a data-leak site, which complicates notification obligations under GDPR / HIPAA because no public dump occurs.

Stay patched, back up offline, and never pay the ransom – payment only fuels the next wave.