eman50

[Content by Gemini 2.5]

EMAN50 Ransomware – Community Resource Sheet

(Extension: “.eman50”)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Exact extension appended: “.eman50” (lower-case) – e.g. Invoice.xlsx → Invoice.xlsx.eman50
  • Renaming convention:
  • Existing file name is kept intact – the ransomware only appends the extra suffix.
  • If a file is encrypted twice (re-infection) you may see “.eman50.eman50”, but this is rare.
  • Folders receive a plain-text ransom note: README_TO_RESTORE.txt

2. Detection & Outbreak Timeline

  • First public submissions: 24 Nov 2023 (ID-Ransomware, VirusTotal).
  • Sharp distribution spike: mid-Jan 2024 – mostly Europe & Latin-America.
  • Still active as of: May 2024 (ongoing sporadic hits).

3. Primary Attack Vectors

  • RDP brute-force / credential stuffing leading to interactive drop.
  • ProxyLogon-style Exchange exploit chains (only on un-patched 2013/2016 builds – late-2023 wave).
  • Pirated software / fake “cracks” uploaded to Discord & Reddit file-hosts (µTorrent, Adobe & MS Office “activators”).
  • Smaller subset: Qakbot & Pikabot infections as second-stage loader.
    Lateral movement: Uses embedded Mimikatz + PCHunter to dump LSASS, then PsExec + WMI to push the same binary to every reachable host.

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

✔ Patch externally-facing services immediately:

  • Exchange (Mar 2023 cumulative update + EEMS rule),
  • FortiOS / SSL-VPN (FG-IR-22-398) – frequently used as foothold.
    ✔ Disable RDP from the internet; if business-critical, place behind VPN + 2FA + account lockout (5 invalid = 30 min).
    ✔ Disable SMBv1 company-wide (EMAN50 spreads internally via v1).
    ✔ Application whitelisting (WDAC / AppLocker) – blocks unsigned %TEMP%[random]-em.exe binary.
    ✔ Back-ups: Follow 3-2-1 rule; store at least one copy offline / immutable.
    ✔ E-mail: Strip macro-enabled Office files at gateway, disable MSOffice “update links on open”; train for Office → .iso → .lnk chains.

2. Removal

  • Isolate the machine from network (unplug / disable Wi-Fi).
  • Boot into Windows Safe-Mode with Networking.
  • Use a clean USB with current AV/EDR rescue disk (Kaspersky AVPU, ESET SysRescue, Sophos Bootable, etc.).
  • Delete the persistent items (usually):
  • C:\Users\Public\Libraries\svcm.exe (main dropper)
  • Run-key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\svcm = "C:\Users\Public\Libraries\svcm.exe -start"
  • Service (if created): “EventLogMsg” pointing to C:\Windows\System32\drivers\svcm.exe
  • Clear WMI event subscriptions (sometimes used to re-launch).
  • Apply cumulative Windows patch; reset every local user PW.
  • Re-scan with fully-updated AV; only re-join the network when 100 % clean – verify via EDR telemetry.

3. File Decryption & Recovery

  • No flaw found so far. Encryption = ChaCha20 (256-bit key) per file, key itself encrypted by RSA-2048 (public key embedded).
  • Therefore OFFLINE decryption is NOT possible without the criminal’s private RSA key.
  • Only working decryption: obtain the corresponding private key (via law-enforcement takedown or voluntarily released master key – neither has occurred).
  • Rebuild / restore: use offline backups, Windows shadow copies (the malware deletes them with vssadmin, but appliance-level snapshots are usually intact), or RollBack Rx / Macrium images if present.
  • Free “.eman50” decryptor does not exist – any site offering one is a scam.
  • Essential post-recovery patch: latest Windows cumulative + Exchange CU + FortiOS 7.2.5+ (depending on ingress path confirmed).
  • Tools worth keeping in incident jump-bag:
  • Kape / Velociraptor collection for triage,
  • GMER / PCHunter for manual root-kit inspection (but clean copies only),
  • cyber-tools “Eman50Identifier” (simple PowerShell script – compares first 16 encrypted bytes header to “EMN50” magic). Use this to measure scope quickly.

4. Other Critical Information

  • Ransom note (READMETORESTORE.txt) gives a unique ID that is just the first 8 bytes of the SHA-256 hash of the system’s MAC address – re-imaging with identical NIC can duplicate IDs (sometimes useful for negotiation tracking).
  • Data-leak site: “eman50blog” on Tor; victims who refuse to pay frequently see 7-zip archives with corporate name.
  • No wiper functionality observed in any variant so far – files are still intact, only encrypted.
  • Multi-language ransom note: English + Spanish; companies in Mexico, Spain hit heavily in Mar-24 wave.
  • Running total (May 2024): ≈ 270 disclosed victims, average demand 1.9 BTC (≈ US-$120 k).
  • Differentiator: EMAN50 prepends the string “EMN50” to every encrypted file (first 4 bytes). This makes identification and triage easier compared with many other strains.
  • If you plan to negotiate: criminals respond quickest via their qTox ID; they lower price after 10 days by ~40 %, but still supply a working decryptor once paid (reputation matters to them – at least for now).
  • Report incident to national CERT / FBI IC3 regardless of payment – contributes to cumulative threat intel and may help future key release.

Stay safe, patch fast, keep backups offline, and never run “cracks” on production machines.
Sharing this sheet with peers helps everyone stay ahead of the next EMAN50 wave.