ethan

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The Ethan ransomware appends the literal string “.ethan” as a secondary extension, leaving the original file extension intact (e.g., Budget2024.xlsx.ethan, presentation.pptx.ethan).
  • Renaming Convention: Files keep their original base name + original extension, then “.ethan” is simply tacked on. No email address, ransom code, or random hex string is inserted.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples uploaded to public multi-scanners on 18-Jan-2021; notable spike in submissions and victim forum posts between 25-Jan-2021 and 05-Feb-2021. Small clusters still observed through Q2-2021 but no large campaigns since summer 2021.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing emails with ISO/IMG or password-protected ZIP attachments containing “Activision.exe” or “PDFConverter.exe” – both are the Ethan dropper.
  2. Exploitation of unpatched Windows SMB (EternalBlue / MS17-010) after lateral movement by an earlier loader.
  3. RDP brute-force → manual deployment of “ethan.exe” in C:\Users\Public.
  4. Supply-chain compromise of a South-East-Asian freeware “PDF combine” utility (vendor name withheld) during Dec-2020 – Jan-2021 period; installer pulled Ethan as a second-stage payload.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Apply Microsoft’s MS17-010 patch (or enable automatic updates) to kill the EternalBlue vector.
    – Disable SMBv1 at the organisational level via GPO:
    Computer Configuration > Policies > Administrative Templates > MS Security Guide > “Enable SMB1 protocol” = Disabled.
    – Enforce 2-factor authentication on all RDP / VPN gateways; use strong, unique passwords and lock-out policies.
    – Restrict e-mail attachments: block ISO, IMG, and password-protected ZIP at the gateway, or at minimum force macro/VBE scanning inside ISO.
    – Use application whitelisting (WDAC/AppLocker) to block unsigned binaries launched from %PUBLIC%, %TEMP%, or user-writable folders.
    – Segment networks (VLANS) and disable RDP if unused (close TCP/3389).
    – Maintain offline, password-protected backups (3-2-1 rule) – Ethan deletes Windows shadow copies (vssadmin delete shadows /all) and overwrites accessible NAS shares.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Physically isolate the machine(s) from network (pull cable / disable Wi-Fi) to stop further encryption or lateral movement.
  2. Boot into Safe Mode with Networking.
  3. Run a reputable AV/EDR full scan. Current detection names:
    – Microsoft: Ransom:Win32/Ethan.A
    – ESET-NOD32: Win32/Filecoder.Ethan.C
    – Sophos: Troj/Ransome-Ethan
  4. Manually delete the persistence entries documented in samples:
    – Scheduled task \Microsoft\Windows\RasMobManager\EUpdater pointing to C:\Users\Public\ethan.exe.
    – Registry run key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run “PDFActivator”="%Public%\ethan.exe".
  5. Delete the dropped binaries: %Public%\ethan.exe, %ProgramData%\dllhost.exe, and any copies in C:\PerfLogs.
  6. Reboot normally and re-run AV scan to confirm no residual artefacts.
  7. Prior to data restoration, patch the ingress vector (e.g., MS17-010) or you will be re-encrypted within hours.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Ethan uses a custom ChaCha20 key per file, followed by RSA-2048 encryption of the ChaCha20 key. The threat-actor keeps the RSA private key offline. Therefore, NO free public decryptor exists. File recovery without paying the ransom is only possible if:
    – You have intact, offline backups.
    – Shadow copies survived (rare – the malware deletes them).
    – System Restore Points were stored on a separate, unmapped volume.
    – Victims can try standard undelete / file-carving tools (PhotoRec, R-Studio) to locate pre-encryption copies, but success rate is low because Ethan overwrites files in place.
    – Law-enforcement seized some backend servers in March-2021; a handful of victims with proof of payment obtained a working RSA private key from investigators. General public cannot rely on that.
    Bottom line: Assume files are unrecoverable without backups or ransom cooperation.

  • Essential Tools / Patches:
    – Microsoft MS17-010 Security Update (KB4013389).
    – “EternalBlue DoublePulsar Detection Tool” (free) – scan to confirm host wasn’t back-doored before Ethan drop.
    – Sysinternals Autoruns & Process Explorer for manual clean-up.
    – Kaspersky’s RakhniDecryptor, Emsisoft’s StopDecrypter, and Bitdefender’s “EthanDecrypt” were all tested – none support Ethan as of 2024.

4. Other Critical Information

  • Additional Precautions:
    – Ethan is hard-coded to skip C:\Windows and Russian & Ukrainian locale systems (kernel language check). This does NOT equate to safety; it is still destructive elsewhere.
    – Drops ransom note !!!ETHAN_DECRYPT.TXT on Desktop and every root directory; note instructs e-mail to [email protected] or [email protected], ransom demand typically 0.12 BTC (changed with bitcoin price).
    – Kills SQL & Exchange services before encryption to unlock database files; verify DB integrity after restore.
    – Uses sDelete -p 3 on original files (secure overwrite); forensic recovery chances are lower than average.

  • Broader Impact:
    – Affected >130 mostly small-to-medium companies worldwide in its prime window (Jan-Feb 2021).
    – Combined SMB-worm capability plus manual RDP deployment created “double-tap” intrusions: victims hit by another family (e.g., Dharma) days later – treat all machines as potentially back-doored.
    – Paying the ransom historically provided a working decryptor, executed via -d switch supplied by actor; however law-enforcement discourages payment and there is no guarantee.

TL;DR: Ethan is an SMB-aware, double-extortion ransomware family that adds “.ethan”, deletes shadows, and offers no free decryptor. Patch MS17-010, secure RDP, back-up offline, and remove with standard AV rather than paying if at all possible.