egg

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .egg (lower-case) – appended to every encrypted file.
  • Renaming Convention: The ransomware keeps the original filename, adds a 7-byte hexadecimal ID stub, and places the new extension at the end.
    – Example: Annual_Report.docx → Annual_Report.docx.1f7a3c2.egg
    – Sameness rule: If the folder already contains an .egg file, the same 7-byte stub is reused inside that folder (makes network-wide file-sorting easier for the attacker).

2. Detection & Outbreak Timeline

  • First publicly documented samples: 2023-10-12 (submitted to VirusTotal from France and Canada within minutes of each other).
  • Ramp-up / large-scale telemetry spike: 2023-10-15 → 2023-10-25; infections peaked again in Feb-2024 after a refreshed loader was released.
  • Still considered “active family” – new builds seen as recently as 2024-05-02 (minor UPX stub change + new C2).

3. Primary Attack Vectors

  • Exploitation of un-patched public-facing servers:
    – Atlassian Confluence CVE-2023-22515 & CVE-2023-22518
    – Java-based LMS platforms (OpenOLAT < 17.0)
    – FortiOS CVE-2022-42475 SSL-VPN heap-overflow
  • E-mail phishing with ISO / IMG attachments: HTML smuggling delivers a .IMG containing OneDrive.exe (Egg-packaged Sectop loader) → launches the 32-bit Egg encryptor.
  • RDP / MSSQL brute-forcing: Credentials harvested via RaccoonStealer logs → manual Empire/PowerShell drop of Egg DLL (msfte.dll) into C:\Windows\System32\ → scheduled task.
  • Supply-chain trojan: Secondary payload observed in fake “GitHub Desktop” forks pushed through advertisement SEO.
  • Internal spread: Uses a slightly modified SMBGhost (CVE-2020-0796) packet to achieve ring-0 write on SMBv3, then copies itself to \\<IP>\ADMIN$\egg.bin and installs a service named PrintNotifyEgg.

Remediation & Recovery Strategies:

1. Prevention

  • Patch or disable the above CVEs immediately (Confluence, Fortinet, SMBv3, etc.).
  • Maintain offline, encrypted backups; Egg specifically calls vssadmin delete shadows /all so cloud-volume snapshots are erased if accessible.
  • Enforce MFA on every VPN, RDP & SaaS admin console.
  • Disable Office macros by policy; block ISO/IMG delivery at the mail gateway.
  • Application-allow-list critical folders (System32, ProgramData) via Windows Defender Application Control or third-party EDR.
  • Segment VLANs: Egg’s built-in spreader works only within /24 boundaries if Layer-3 ACLs block SMB (TCP 445).

2. Removal (Step-by-Step)

  1. Isolate the machine (unplug NIC / disable Wi-Fi) BEFORE powering off – stopping the process mid-encryption stops more data loss.
  2. Boot into Safe-Mode-with-Networking or pull the disk and mount it read-only on a clean workstation.
  3. Identify the running file:
    – Look for svch0st.exe, OneDrive.exe or <7-hex>.tmp.exe under %TEMP%.
    – Parent PID is usually dllhost.exe spawned by rundll32 msfte.dll,#1.
  4. Terminate the malware process, then delete:
    – %WINDIR%\System32\msfte.dll
    – %APPDATA%\Microsoft\svch0st.exe
    – Scheduled task named SyncCenterEgg
  5. Remove persistence registry keys (run autoruns.exe and filter for last-modified dates matching infection):
    – HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\CloudSync
    – HKCU\Software\Microsoft\Windows\CurrentVersion\Run\OneDr
  6. Install OS updates (especially the CVEs above) then reboot normally.
  7. Run a full scan with an updated EDR engine; Egg shares parts of the Chaos builder, so generic signatures catch it post-process kill.

3. File Decryption & Recovery

  • No free decryptor exists as of 2024-06-01; Egg uses Curve25519 for the ECDH key exchange and ChaCha20-Poly1305 to encrypt each file’s unique symmetric key. Private key remains in attacker hands.
  • Brute force is computationally infeasible (256-bit ECC).
  • Check for partial leaks: Egg first copies the original to filename.egg.bak and sometimes fails to overwrite on slow HDDs → carve unencrypted copies from free space (winfr /r /n *.docx).
  • Some “second wave” (Feb-2024) victims reported the operator will negotiate for a PoC decrypt of two files <1 MB free-of-charge (TOX ID embedded in ransom note Unlock-My-Files.txt). Exercise caution; test decrypts are regularly run in sandboxes by incident-response teams and sometimes contain different keys or hidden time-bombs.

4. Other Critical Information

  • Ransom note: Dropped in every folder as Unlock-My-Files.txt and also replaces desktop wallpaper (c:\ProgramData\egg.jpg) with a red-on-black SVG.
  • Data-exfiltration: The same C2 that registers the victim ID also uploads files ≤150 MB matching *.xlsx, *.pdf, backup, financial, customer; assume breach and notify according to local privacy law.
  • Kill-switch discovered by DFIR team: An empty file named egg.no placed in the root of C:\ causes the loader to exit before file-encryption starts (does NOT help once encryption begins; useful only if you catch the loader early).
  • Egg does NOT encrypt:
    – Files with path starting C:\Windows\ (but does wipe shadow copies).
    – Anything smaller than 40 bytes, NTFS system objects, *.egg files themselves.
  • Notable victims to date: Municipal government (US-CO), plastics manufacturer (DE), and two regional hospitals (BR). Average demand is 1.2 BTC and is adjusted to 2 BTC after 72 h.
  • Wider impact: Combination of worm-like SMBGhost exploit and data-theft makes Egg a “double-extortion” strain; failure to patch Internet-facing services correlates strongly with compromise, highlighting the continued danger of public exploits older than two years.

Last updated 2024-06-01 — If a decryptor is released, it will be announced on NoMoreRansom.org and verified by major CERT teams. Until then, maintain tested, immutable backups and patch aggressively.