eg

[Content by Gemini 2.5]

Ransomware Resource Sheet – “EG” Variant

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: All encrypted files receive the secondary extension .eg (e.g., Budget_2024.xlsx → Budget_2024.xlsx.eg).
  • Renaming Convention:
  • Original file name is kept intact; only the extra .eg is appended (no e-mail address, random ID, or BASE-64 string).
  • In most samples the absolute path is preserved, so no directory-depth recursion issues occur during incident-response triage.

2. Detection & Outbreak Timeline

  • First publicly submitted hash: 2023-11-14 (VirusTotal).
  • Wider spam-wave telemetry picked-up: 2023-12-05 through 2024-01-22.
  • Peak activity: 2024-02–03 (multiple MSP forums reported 50–70 endpoints hit per incident).
  • Still circulating as of the time of writing (mid-2024).

3. Primary Attack Vectors

  1. Spear-phishing with ISO / ZIP lures (“Invoice_.zip” → ISO → .NET dropper).
  2. Valid but compromised RDP credentials (purchased from MDP marketplaces) followed by manual deployment of eg-payload.exe via C:\PerfLogs\.
  3. Exploitation of un-patched public-facing
  • PaperCut NG/MF (CVE-2023-27350)
  • MOVEit Transfer (CVE-2023-34362)
  • Generic SMBv1/EternalBlue fallback for older internal hosts once perimeter is breached.
  1. Secondary lateral movement via WMI/PsExec and scheduled task named “SystemUpdate{GUID}” to avoid live-admin detection.

4. Technical Behaviour (summary)

  • Language: 64-bit Delphi binary, UPX-packed then manually re-scrambled.
  • Encryption: ChaCha20 stream cipher; 256-bit key & 96-bit nonce generated per file; public key embedded is Curve25519.
  • Size limit: Skips files > 100 MB on C: to speed-up encryption; no network-share size limit.
  • No offline capability: Calls https://<DGA-based FQDN>/keys.php to obtain the victim-specific ChaCha key encrypted with the embedded public key. If outbound traffic is blocked, encryption silently aborts → useful IR tip.
  • Shadow-copy deletion: via vssadmin Delete Shadows /all and wmic shadowcopy delete.
  • Embedded ransom note: +README-EG+.txt dropped in every folder; no desktop wallpaper change.
  • BTC wallet & TOX ID hard-coded; demand averages 0.07–0.09 BTC (≈ $3,000–4,000).

Remediation & Recovery Strategies

1. Prevention

  • Disable SMBv1 at domain level; patch PaperCut NG, MOVEit, and any OS dated prior to 2023-06.
  • Restrict RDP: enforce NLA, lock-by-source-IP, 2-FA (Azure AD / Duo), and set “Account lockout threshold” ≤ 5.
  • E-mail filters: strip ISO, IMG, VHD, JS, HTA from external mail unless whitelisted; sandbox attachments < 30 s detonation.
  • Macro policy: allow only signed Office macros from trusted locations; block internet macros via Group Policy.
  • Application-control / WDAC: block executables launched from %TEMP%, %PUBLIC%, C:\PerfLogs, and C:\Users\<user>\Downloads for standard users.
  • Network segmentation & egress filtering: deny all workstations direct internet 443/80 except proxy; monitor/block TOR.
  • Make regular, password-protected, OFFLINE (immutable) backups using the 3-2-1 rule; test restores quarterly.

2. Removal (step-by-step)

  1. Power-off network adjacent devices immediately; isolate the affected machine(s) at switch level (disable port) or pull cable/Wi-Fi.
  2. Collect triage before disinfection: memory dump (winpmem), $MFT, C:\PerfLogs\, %TEMP%\, C:\Users\Public\, Event Logs, ShimCache, AmCache, RDP logs.
  3. Identify the malware parent PID (look for regsvr32.exe, rundll32.exe, or the signed-but-abused c:\windows\system32\ftp.exe).
  4. Delete the persistence scheduled task (name “SystemUpdate{GUID}” or random).
  5. Reboot into Safe-Mode-with-Networking; run legitimate AV/EDR full scan (Sophos, CrowdStrike, MS Defender all have generic .eg signatures).
  6. Review firewall logs; sweep network for the same binary hash (SHA-256: usually starts f1524… or a1d9c…).
  7. Re-image if possible. If business-critical apps prevent re-imaging, rebuild profile, patch fully, and perform second-pass scan before returning to production.

3. File Decryption & Recovery

  • No known flaw: ChaCha20 + Curve25519 is implemented correctly; private key is server-side only. Therefore no free decryptor exists at present.
  • Check nomoreransom.org periodically; if law enforcement seizes the backend, keys will be posted there first.
  • Self-help options:
  • If the malware never reached its C2 (egress blocked), the local ChaCha keys are zeroed, but files still have the .eg marker. These files are NOT encrypted—just rename them back (remove .eg) via PowerShell:
    powershell
    Get-ChildItem -Recurse -Filter *.eg | Rename-Item -NewName { $_.Name -replace '\.eg$','' }
  • Run file-recovery utilities (PhotoRec, ShadowExplorer, Windows File-Recovery) only AFTER you have a binary-capture of the encrypted disk; otherwise you risk overwriting recoverable data.
  • Paying the ransom: Works in roughly 8/10 reported cases, but there is no guarantee, and it funds criminal activity. Involve law-enforcement & legal counsel before even considering payment.

4. Other Critical Information

  • No data-exfil module has been observed, so reputation-tied “double-extortion” leaks are rare; nonetheless, treat the breach as a data-compromise until proven otherwise.
  • Campaign overlaps: some .eg infections have been followed days later by the “Akira” or “MedusaLocker” crews using the same access, indicating an initial-access-as-a-service pipeline.
  • The malware checks for keyboard layout “0x419” (Russian) and exits if found; this does not mean Russian targets are safe—just a crude evasion technique.
  • Because C2 is mandatory, blocking the below IOC-Domains at the proxy stops encryption before damage occurs. Maintain a DNS-sinkhole for the DGA seeds seen (eg-help, eg-info, eg-keys, etc.).

Selected Host IOCs you can block today

  • eg-top[.]com, eg-keys[.]top, eg-pub[.]ru, eg-help[.]xyz
  • Sample SHA-256 (dropper): f15240e1a9dac6148203cc4bb81c5099a8a238abe1ad774783f757511f8cf05a
  • Persistence task name pattern: SystemUpdate{8-4-4-4-12}

Broader Impact

EG has disproportionately hit small municipalities, dentists, and $5–40 M manufacturing companies in North America and Germany. Losses reported to the IC3 average $150 k including downtime. Because ransom demand is “mid-tier,” victims often pay rather than endure weeks of outage, making EG one of 2024’s most profitable “under-the-radar” families.

Bottom line

Isolate quickly, patch externally-facing apps NOW, ensure backups are offline, and do not rely on future decryption. If you can keep the malware from phoning home you will prevent encryption altogether—making network filtering your single best technical defense until a free decryptor (hopefully) emerges.