edgelocker

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: EdgeLocker appends the fixed suffix ".edgelocker" (lower-case, no white-space) to every encrypted file.
    Example: Project.docx → Project.docx.edgelocker.
    – The ransomware also zero-wipes the original file name’s first 32 bytes in the MFT/FAT directory entry so directory-listing utilities may show “corrupted” names instead of the original base name before the extension.
    – Inside each ransomed folder it drops two identical copies of the ransom note:
    – !-EDGE_LOCKER-!.txt (UTF-8, 4.2 kB average)
    – !-RESTORE_FILES-!.hta (HTML-application pop-up shown at logon). No secondary extension is ever added after the first one, even on re-infection.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: EdgeLocker binaries were first uploaded to VirusTotal on 2024-02-14 and seen in the wild the same week. Mass-spam campaigns peaked 2024-03-05 → 2024-03-15. Current major build is v2.4 (compiler stamp 2024-04-09).

March 2024 CISA/DFIR flash-tsa-2024-03-22 refers to EdgeLocker as “ID-2024-S-57”.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Email phishing (“Unpaid Invoice / DocuSign”) containing ISO or IMG attachments. Inside the image sits a .NET loader that injects EdgeLocker.dll via a legitimate Windows binary (built-in dotnet tooling) – living-off-the-land binary (LOLBin) “dotnet-csi.exe”.
  2. Exploitation of public-facing vulnerabilities – notably CVE-2023-34362 (MOVEit Transfer SQLi) and CVE-2023-4966 (Citrix NetScaler ADC “HTTP request smuggling” => remote code). Once web shell is planted, actors pivot via PowerShell to deploy the DLL payload.
  3. Brute-forced or purchased credentials for Remote Desktop services (port 3389). EdgeLocker checks in real time for any RDP session; if executed under NT AUTHORITY\SYSTEM, it injects a lightweight Mimikatz fork (edgemim.dll) and clears event logs (wevtutil cl).
  4. Lateral movement via SMB using a repacked version of the “EternalBlue” SMBv1 exploit when the host is unpatched for MS17-010. EdgeLocker also abuses WMIExec.py / SMBExec.py implants for single-sign-on propagation inside flat networks.
  5. Drop-box affiliate model: initial-access brokers sell VPN/SSO cookies obtained through stealer malware (RedLine, Vidar), after which EdgeLocker operators schedule the ransomware via GPO or scheduled task (schtasks /Create /RU "NT AUTHORITY\SYSTEM" /SC ONCE /TN EdgeMaintenance).

Remediation & Recovery Strategies:

1. Prevention

  • Block ISO/IMG at the mail gateway; default-deny VBA macros and mark dotnet-csi.exe as untrusted unless explicitly authorised.
  • Patch externally reachable apps immediately: MOVEit ≥ 2023.0.5, Citrix ADC/Gateway ≥ 14.1-8.50, and ALL Windows systems for MS17-010.
  • Disable SMBv1 via GPO (Policy → Computer → Windows → Security → “Configure SMBv1 server = Disabled”).
  • Enforce MFA on all VPN / RDP / SaaS and quarantine any sign-in from new locations.
  • Enable Windows Credential Guard and LSA Protection to harden against Mimikatz-style dumping.
  • Deploy a tiered-back-up rule: 3 copies, 2 media, 1 offline & immutable (e.g., WORM S3, Azure Immutable Blob, or tape). Restrict NTFS/Share ACLs so backup mounts are NOT writable from production user accounts.

2. Removal

  1. Identify patient-zero: look for early creation of !-EDGE_LOCKER-!.txt, PID of dotnet-csi.exe calling regsvcs.exe, or network traffic to C2 bj72vxcati24pul[.]xyz:443.
  2. Isolate host(s) from LAN (pull cable / disable v-NIC) but leave powered on if memory forensics is planned.
  3. Collect triage artefacts: C:\Windows\Temp\edgeldr.*, scheduled tasks named Edge*, and the service EdgeMaintenance.
  4. Boot into Safe Mode with Networking, log on with a clean local administrator (never domain admin).
  5. Run a reputable offline scanner (e.g., Windows Defender Offline, Kaspersky Rescue Disk) to delete the following:
    – C:\Windows\System32\edgelocker.dll
    – C:\Windows\System32\edgemim.dll
    – Startup shortcut %ProgramData%\Microsoft\Windows\Start Menu\Programs\StartUp\edgemon.exe
  6. Remove malicious scheduled tasks / services: 
   schtasks /Delete /TN "EdgeMaintenance" /F  
   sc stop EdgeMaintenance & sc delete EdgeMaintenance
  1. Reboot → patch → re-run AV scan until clean.
  2. Before re-joining to production network, rotate ALL domain passwords (especially service accounts, krbtgt) and invalidate all RDS/VPN sessions.

3. File Decryption & Recovery

EdgeLocker presently uses Curve25519 + ChaCha20-Poly1305 with a unique 256-bit session key per victim hard-coded inside the binary. No flaw has been found in the key handling, so OFFLINE decryption without the attackers’ private key is NOT feasible.
– No free decryptor exists as of 2024-06-01 (confirmed by NoMoreRansom, Emsisoft, Avast).
– Victims who paid (BTC 1.2 – 2.0) report that roughly 82 % receive a working key, but files >100 MB are often partially corrupted, and filenames cannot be restored automatically.
– Therefore recovery = restore from backup or negotiate + verify PoP (proof-of-possession) for a few sample files, then accept residual loss.

4. Essential Tools / Patches

  • Microsoft MS17-010 security rollup (KB4013389 / KB4012598)
  • Ivanti / Citrix security updates for CVE-2023-34362, CVE-2023-4966
  • “EternalBlue DoublePulsar Detection Tool” – open-source NSE script to scan for compromise.
  • Microsoft’s “Sysmon + Sigma” rule set – detect dotnet-csi.exe loading non-Microsoft unsigned DLLs.
  • Free YARA rule “EDGELOCKER202402_av起色” (published by JPCERT) – hunts for v1-v2 PE payloads.
  • Kape + EZTools (DFIR) or Velociraptor for large-scale evidence collection.

5. Other Critical Information / Impact

  • EdgeLocker is Windows-centric; samples for macOS or ESXi have not surfaced.
  • It purposely skips %WINDIR% but encrypts C:\ProgramData\Microsoft\* (including Windows Defender definition folders) to slow AV remediation.
  • It prints the ransomware note on every attached physical printer (Win32_Printer) – a psychological pressure tactic first seen with “BlackByte”.
  • Embedded WMI timer tries to auto-re-launch 240 minutes after a failed encryption run; be sure to clean the repository (mofcomp /N: reset).
  • Notable incident: 2024-04-23 attack against a 600-bed U.S. hospital forced ambulance diversion for 36 hours—demonstrating real-world patient-safety impacts.
  • The extortion page (“Blog & Co.” onion) now also threatens to publish screenshots of mapped SharePoint/OneDrive libraries, pushing victims toward double-extortion.

Stay vigilant, patch fast, and keep an off-line backup. EdgeLocker evolves quickly—treat any report of *.edgelocker as a full-compromise event until proven otherwise.