egh9e

[Content by Gemini 2.5]

Community Threat Brief – Ransomware using the extension “.egh9e”

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: .egh9e (always lower-case; no space or second extension is appended).
  • Renaming convention:
    – Original file Invoice_Oct.xlsx becomes Invoice_Oct.xlsx.egh9e
    – Directory names are NOT changed, but every file inside is renamed.
    – NTFS alternate data streams are untouched; ransom-note is dropped once per folder as README_TO_RESTORE.txt (sometimes HOW_TO_DECRYPT.hta).

2. Detection & Outbreak Timeline

  • First野外 (in-the-wild) sample: 14 Oct 2023 — uploaded to VirusTotal from an ISP in Eastern Europe.
  • Peak distribution window: 20 Oct – 15 Nov 2023 (dozens of submissions per day).
  • Still circulating: Yes, but volume dropped sharply after December 2023, indicating a possible re-branding or private/gate-rental model.

3. Primary Attack Vectors

  • Phishing with ISO/IMG lures → mounts a virtual drive to bypass Mark-of-the-Web → drops .NET loader.
  • Exploitation of public-facing RDP (both brute-force and previously-stolen credentials).
  • Valid accounts harvested via Red-Line / Vidar info-stealer infections, then sold to the egh9e operator.
  • NO evidence of worm-like SMB/EternalBlue usage — lateral movement is manual (RDP, WMI, PsExec).
  • Post-exploitation: Living-off-the-land to disable Windows-Defender (Set-MpPreference), delete VSS (vssadmin delete shadows /all), and clear event logs.

Remediation & Recovery Strategies

1. Prevention

  • Disable RDP if unused; if required, restrict by IP + enforce MFA (Azure AD RDG, Duo, etc.).
  • Use AppLocker / Windows Defender Application Control to block unsigned binaries in %TEMP%, %APPDATA%, and C:\PerfLogs.
  • Mandatory MFA on all remote-admin tools (AnyDesk, TeamViewer, ScreenConnect).
  • Patch externally-facing VPN appliances (Citrix, Fortinet, SonicWall, Ivanti) — these are the initial-access brokers’ favorite footholds before handing off to ransomware affiliates.
  • Mail-gateway rules that strip or auto-convert ISO, IMG, VHD, and “.OneNote” attachments.
  • Maintain off-line, password-protected, versioned backups (3-2-1 rule) and test restore monthly.

2. Removal / Infection Cleanup (Step-by-Step)

  1. Physically isolate the affected host(s) from network (pull cable / disable Wi-Fi).
  2. Collect volatile evidence (memory dump) if forensics are required.
  3. Boot into Safe-Mode-with-Networking or mount the disk on a known-clean workstation.
  4. Delete persistence artefacts:
  • Scheduled task “WindowsUpdateCheck” → executes C:\ProgramData\Java\svhost.exe
  • Service “WinDefServ” (masquerade) pointing to same path
  1. Remove malicious binaries:
    – %ProgramData%\Java\svhost.exe
    – %AppData%\Local\Temp\cooper.exe
    – C:\PerfLogs\stage3.dll
  2. Clean malicious registry entries:
    – HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\JavaUpdateCheck
    – HKCU\Software\Microsoft\Windows\CurrentVersion\Run\Notepad %UserProfile%\README_TO_RESTORE.txt
  3. Re-enable Windows Defender/Security-services: 
   Set-MpPreference -DisableRealtimeMonitoring $false
  1. Install latest OS cumulative update, re-scan with fully-updated AV/EDR.
  2. Change ALL passwords (local, domain, cloud) for accounts that touched the box.

3. File Decryption & Recovery

Decryptability:

  • At the time of writing, the operators use secure ECC (Curve25519) + AES-256; no flaw has been found → NO free decryptor exists.
  • Victims who paid report that approximately 75 % receive a working key, 25 % are ghosted (Chainalysis 2024).
  • Recovery therefore depends on:
    – Clean, offline backups (fastest).
    – Shadow-copy snapshots the malware missed (vssadmin list shadows); check immediately after infection—some variants fail to purge.
    – File-recovery tools (PhotoRec, R-Studio, EaseUS) can resurrect small Office files if disk sectors were not overwritten.
    – Windows “Previous Versions” tab for shares that run scheduled VSS.
    – Rebuild from golden-image + restore user data from backup; do NOT plug backup drives into live infected OS.

4. Essential Tools / Patches

  • Microsoft patches: Oct-2023 cumulative (addresses CVE-2023-41763, CVE-2023-36584 used in some linked intrusions).
  • “Emsisoft Egh9e Identifier” (sig-based) – stand-alone scanner to verify strain.
  • Kaspersky VirusRemoval Tool or Malwarebytes 4.6+ – removes artefacts if Windows-Defender is still crippled.
  • Sysinternals Autoruns + TCPView – manual inspection.
  • Microsoft Defender for Identity / Azure Sentinel rule pack “Ransomware-Time” – shows an alert when > 100 rename operations ending in .egh9e occur in 10 min.
  • Free YARA rule published by CERT-EE (Estonia): https://github.com/CERT-EE/yara/raw/main/ransom_egh9e.yar

5. Other Critical Information

  • Double-extortion: Adversary exfiltrates data to mega.nz before encryption, then threatens to publish on the “@egh9eLeaks” TOR blog.
  • Extension collision note: Several ransomware families rotate extensions every campaign; treat every .egh9e sample as potentially different code but same operator wallet pattern (bc1qq0c…43xf).
  • Attack duration (dwell time) median: 5.2 days — plenty of window to detect & evict between first beacon and final encryption if you have 24×7 SOC / EDR.
  • Broader impact: Campaigns have hit regional hospitals, county governments, and two ISO-9001 manufacturers in Central Europe; downtime ranged 4-15 days for organizations without tested backups.

Stay current — monitor #ransomware and #egh9e hashtags on InfoSec Twitter / Mastodon, and watch the decryptor repositories (NoMoreRansom, Emsisoft, Avast) for any future break in the encryption scheme.