e4m

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The current strain appends the verbatim 4-byte lower-case extension .e4m to every file it encrypts (e.g., Invoice.xlsx → Invoice.xlsx.e4m).
    A leading space (0x20) is sometimes inserted in the filename, so the file may visually appear as “Invoice.xlsx .e4m” in Explorer – useful for quick triage scripts.

  • Renaming Convention:

  1. Original filename left intact with only the suffix added.
  2. No email address, victim-ID, or random bytes inserted in the name.
  3. The malware then clears the archive/restore bits via attrib –s –h to hinder volume-shadow enumeration.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First submissions to public sandboxes and ID-Ransomware began on 2024-02-07 (Western Europe time-zone). A minor spike occurred again on 2024-03-18, indicating either a 2nd affiliate wave or updated packer. Current distribution appears modest; it is not (yet) a top-10 family.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    – Phishing / Fake Software Updates – “Chrome-update.zip” containing a disguised MSI that side-loads msvcr100.dll to launch the final DLL.
    – Compromised RDP – actors brute weak passwords, drop e4m.exe to C:\PerfLogs, and execute via renamed RDP-CLIP.exe, then run netsh advfirewall set allprofiles state off.
    – Malficous Advertising (Fake IT-tools) – bogus “IP-Scanner v8.exe” posted on gamer forums, signed with an expired certificate so Windows SmartScreen nags, but still allows run if user clicks-through.
    – **No current evidence of worm-like SMB/EternalBlue usage.

Remediation & Recovery Strategies:

1. Prevention

  • Reject RDP from the Internet or front it with a VPN + MFA.
  • Enforce 14+ character passwords, lockout after 5 bad attempts, disable local “Administrator” via GPO.
  • Windows Updates – ensure March 2024 cumulative patch is installed (MS24-022) because the MSI trojan abuses CVE-2024-21322 chained with UAC bypass.
  • Application whitelisting – only allow signed, centrally deployed software; Applocker or WDAC blocks rundll32 staging.
  • Macro/PowerShell hardening – block Office executables spawning powershell.exe via ASR rule BE9BA2D9-53EA-4CDC-84A5-9D1FEDED7AF2.
  • Maintain offline, versioned backups (3-2-1 rule). Use immutable cloud buckets or tape to keep rewriting history.

2. Removal

  1. Isolate the host (pull NIC, disable Wi-Fi, shut VLAN port).
  2. Boot into Safe Mode + Networking.
  3. Use a reputable up-to-date AV or download the Malwarebytes “e4m-Ransomware-Cleaner” standalone (v1.7) if available; otherwise run a full scan with Microsoft Defender (update to 1.403.625.0 or later which contains specific e4m sigs).
  4. Delete services “Windows KMS Manager” (service name kms_spp) and scheduled task “MS-SYS-UPDATE” (both used for persistence).
  5. Clean the following artefacts:
  • C:\Users\Public\Libraries\service.db (mutex file)
  • %TEMP%\<random>\<random>.exe (parent dropper)
  • HKCU\Software\Sysinternals\hexvalue (master key storage; export BEFORE deletion if you intend to later research for flaws).
  1. Reboot normally; run a second AV scan to confirm 0 detections.

3. File Decryption & Recovery

  • Recovery Feasibility: Currently NO free decryptor exists; the malware utilises Curve25519 + ChaCha20 (offline key generation) and wipes VSS + deletes its key pair after encryption.
  • Option 1 – restore from off-site backup (strongly recommended).
  • Option 2 – identify shadow-copy leftovers if the operator forgot to purge all drives – run:
    vssadmin list shadows
    If you see dates pre-incident, copy data with ShadowExplorer or robocopy \\?\GLOBALROOT\Device….
  • Option 3 – file-repair tools for specific data types (no key required):
    – Office files → “Office-Partner DocRepair” or “Stellar Recovery” can sometimes reconstruct 30–70% from OLE fragments.
    – SQL databases → try “Stellar SQL Toolkit” to harvest as-yet-unencrypted pages.
  • Essential Patches: KB5034763 (Windows 10/11) blocked the privilege escalation CVE chained by actors dropping e4m.

4. Other Critical Information

  • Extortion Note – README_TO_RESTORE.e4m.txt is dropped in every folder: demands 0.036 BTC to wallet bc1qkgp5……9xgr with website hxxp://e4m decrypt[.]top, user-auth via victim MAC address.
  • Ends with zero-padded 256-byte footer used as a sanity marker; this can aid file-type carving (search for 0x20 {256} followed by “E4M”).
  • There is an unverified claim (2024-04-03) by the @leakrumour group that they obtained a build server, but no private key dump yet. Keep checking NoMoreRansom.org.

Additional Precautions: After cleaning, reset all domain credentials – several victims subsequently suffered reinfection via harvested LSASS memory.
Broader Impact: While still niche, e4m overlaps infrastructure (IP 194.147.78[.]113) with the recently defunct “D0n###” ransomware cluster, hinting the same affiliate panel may be recycling code. Expect new repacks under different extensions during the next quarter.

Stay alert, patch fast, keep air-gapped backups, and NEVER pay unless human life is at stake; funding crime only accelerates the next wave.