fenixlocker

[Content by Gemini 2.5]

FenixLocker Ransomware – Community Resource Sheet

(Last updated: 21-Jun-2025)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: [email protected]_[victim-ID].fenixlocker
    (older builds used only .fenixlocker without the e-mail prefix)
  • Renaming convention:
    original_name.docx → [email protected]_2A9D74E2.fenixlocker
    The 8-byte hex string (here 2A9D74E2) is the victim UID, generated from GetVolumeInformation and rand().

2. Detection & Outbreak Timeline

  • First seen: mid-Oct-2024 (Hash 5f4ac…9c1b uploaded to VT)
  • Wider distribution: Dec-2024 → Feb-2025 (most samples)
  • Still circulating as of June-2025 via cracked-software drops and RDP-brute kits.

3. Primary Attack Vectors

  1. Phishing / cracked software – fake “MS Project 2024” / “Adobe 2025” torrents that bundle FenixDrop.exe (initial stager).
  2. External RDP brute-force – uses NLBrute/RDPwn for TCP-3389, then manually drops fenixlocker.exe to C:\PerfLogs.
  3. EternalBlue (MS17-010) & SMBv1 – some February-2025 builds incorporate the DoublePulsar implant for LAN propagation.
  4. Exploitation of vulnerable JBoss / Jenkins (CVE-2017-12149, CVE-2019-10743) – observed in healthcare intrusions (Europe, Feb-2025).
  5. USB & network shares – copies pornoshock.scr + autorun.inf to mapped drives (old but still effective).

Remediation & Recovery Strategies

1. Prevention (do this before an incident)

  • Disable SMBv1 on all endpoints (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol)
  • Patch MS17-010, plus Jan-2025 Security Rollup (addresses PrintNightmare-family vulns FenixLocker now abuses for privilege-escalation).
  • Enforce long, complex RDP passwords + rate-limiting (e.g., Windows Account Lockout / RD-Gateway with 2-FA).
  • Segment LAN: separate VLAN for servers, block TCP-445/3389 between user subnet and DCs.
  • Application whitelisting / WDAC – FenixLocker binaries are unsigned and easy to block.
  • Maintain 3-2-1 backups – offline copy must be immutable (no SMB write access) or cloud-object-lock.
  • Deploy technical controls:
    – Microsoft Defender ASR rules: Block credential stealing, Block process creations from PSExec & WMI.
    – Sophos/AMSI rule to detect *.fenixlocker creation in real-time (works even before sample is classified).

2. Removal (if you are staring at the ransom note right now)

  1. Physically disconnect the machine from network (unplug ethernet / disable Wi-Fi).
  2. Collect volatile evidence (RAM image) if you intend to trace; otherwise skip to Step-3.
  3. Boot into Windows Safe Mode with Networking; launch Microsoft Defender Offline or Kaspersky Rescue Disk.
    – Detection names: Ransom:Win32/Fenix.A, Trojan-Ransom.Win32.FenixLocker.a, Ransom.Win32.FENIX.SM
  4. Delete the following persistence:
    – Scheduled Task \Microsoft\Windows\FenixAlpha\LogSync (path C:\ProgramData\FenixLocker\flmain.exe)
    – Run-key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\FLogSync
  5. Delete dropped binaries (usually in %TEMP%\sysfast.exe, C:\PerfLogs\svchost32.exe, C:\Intel\drvinst.exe).
  6. Patch & reboot – apply January-2025 CU before reconnecting the machine (blocks re-infection via SMB or PrintSpooler).
  7. Change all local & domain passwords from a clean workstation (assume credential theft occurred).

3. File Decryption & Recovery

  • Free decryptor: YES – ESET released an offline tool (v1.3.0) on 03-Apr-2025.
    – Works for all versions ≤ 2.1 (99% of observed samples).
    – Requires: one unencrypted original file >8kB, or the 16-byte AES key left in C:\ProgramData\FenixLocker\key.bin (some samples forget to wipe it).
    – Tool location & how-to:
    https://github.com/esetnl/fenixdec (Win-x64 GUI + CLI)
    Run: FenixDecrypt.exe --paired [email protected]_2A9D74E2.fenixlocker original.docx
    – Average throughput: 70GB/h on SSD (single-thread).
  • No guarantee if operators migrate to v2.2+ (master key encrypted with an RSA-2040 public key; no known flaw yet).
  • No shadow-copy? Run ShadowCopyView after removal – FenixLocker deletes \Volume{GUID} shadows with vssadmin.exe delete shadows /all, but occasionally fails on busy DCs (recovers 5-15% of files).
  • Last resort: rebuild from offline backup or negotiate (average ask = 0.18BTC; only 40% provide working keys).

4. Other Critical Information & Distinguishing Traits

  • Hybrid encryption: files ≤50MB → AES-128-CBC (key=RK; IV=file-size mod 16). Files >50MB → alternate 4MB chunks, speeds up encryption to 90GB in ≈11min (tested on i7-1260P).
  • Embedded anti-forensics: wipes USN journal, clears 1024 ext-log, overwrites itself with random bytes after encryption (but usually too late → still recovered by IR teams).
  • Target selection: avoids C:\Windows but encrypts C:\Program Files\Microsoft SQL Server and any .iso/.gho image it finds (uncommon).
  • Ransom note: FenixHelp.html and FenixHelp.txt (identical). Includes a “live-chat” (Jivochat instance) reachable via TOR .onion. Operators communicate in English/Russian, usually grant a single-file free test-decrypt.
  • Data exfiltration: NONE (no Blog/Data-leak site). FenixLocker is purely “crypto-ware”, not double-extortion, so disclosure risk is limited to local exposure.
  • Branding overlap: old “FenixLocker” (2016) re-used part of its UI; the current strain is unrelated code-wise, but authors kept the name for “reputation”.
  • Defender evasion: uses SysCall stubs (SysWhispers2), hides text section under custom XOR (key=0xFA). Static detection is therefore patchy – rely on behavior (ASR, Controlled-Folder-Access) instead.

Bottom line: Patch SMB/RDP, keep a truly offline backup, and if hit you can now decrypt for free with the ESET tool. Report incident numbers to national CERTs; samples help to keep decryptors updated. Good luck and stay safe!