eu

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The current ransomware wave appends the literal suffix .eu (lowercase) to every encrypted object.
    Example: Annual_Report.xlsx → Annual_Report.xlsx.eu
    No second extension, prefix, or randomised UID is added, so victims frequently do not notice the change until they try to open a file.

  • Renaming Convention: Files are processed in-place with a single MoveFileExW call after encryption is finished. Each directory also receives one of several capitalised ransom notes (DECRYPT-FILES.txt, HOW-TO-RESTORE.txt, or ReadMe_EU.txt) containing a 40-character victim-ID and a TOR-based negotiation URL ending in “.eu”.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First uploaded to VirusTotal on 2023-11-03; sharp uptick in ID-Ransomware submissions mid-November 2023. Continues as an “opportunity” strain in Q1-2024, often following QakBot / Pikabot infections.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Phishing e-mails with ISO, ZIP or OneNote attachments that drop QakBot → Cobalt Strike → .eu payload.
    • Exploitation of unpatched vulnerability CVE-2023-36884 (Windows Search 0-day used in July 2023 campaigns) when the host was not yet patched.
    • External RDP brute-forcing (TCP/3389) or stolen credentials sold on marketplaces; once inside, living-off-the-land PSExec / WMI to push the encryptor to every reachable machine.
    • Occasionally dropped manually after GootLoader or TrueBot infections in healthcare and legal verticals.

(EternalBlue / SMBv1 is not used by this family; infection chains so far rely on interactive human-operated deployment.)

Remediation & Recovery Strategies

1. Prevention

  • Disable Office macros for Internet-originating documents; enforce “Block all Office files from the Internet” group-policy where feasible.
  • Apply Microsoft’s August 2023 cumulative patch (fixes CVE-2023-36884) and March 2024 updates.
  • Enforce LAPS + 14+ character unique local-admin passwords; restrict RDP exposure behind VPN+2FA.
  • Use Windows Defender Exploit Guard rule “Block executable files running unless they meet a prevalence, age, or trusted list criteria” (ASR rule 01443614-CD74-433A-B99E-2ECDC07BFC25).
  • Segment flat networks; put offline, password-protected Veeam/Commvault repositories on a VLAN without SMB write access.
  • Maintain immutable/off-site backups (S3 Object-Lock, Azure Immutable Blob, tape).

2. Removal

  1. Physically isolate the host (pull LAN or disable Wi-Fi) to stop lateral movement.
  2. Boot into Safe Mode with Networking or use a Windows PE / Linux Live USB if machine is unstable.
  3. Identify persistence:
  • Run autoruns64.exe → filter “Scheduled Tasks” for random-name .ps1, .bat, or rundll32 calling “%TEMP%\`eu`” DLLs.
  • Check Services for items named EUSvc, EuData, or WinDefEuUpd.
  1. Delete malicious binaries (usually C:\Users\Public\eu.exe, C:\ProgramData\*.eu.dll).
  2. Remove ransom notes (DECRYPT-FILES.txt, ReadMe_EU.txt) once samples are preserved for forensics.
  3. Run a fully updated AV/EDR full scan (Defender, SentinelOne, CrowdStrike, Sophos) to clean residual implants.
  4. Patch the exploited vector (macro settings, CVE-2023-36884, RDP) before reconnecting to production VLAN.

3. File Decryption & Recovery

  • Recovery Feasibility: No flaw has been found in the malware’s ChaCha20+ECDH implementation; NO free decryptor currently exists.
  • Victims can attempt to locate shadow copies, Windows File History, Veeam/Vault snapshots, or M365/SharePoint versioning – the ransomware deletes vssadmin snapshots but sometimes misses third-party or cloud-based restore points.
  • Upload a pair of identical plaintext/ciphertext files (≥ 1 MB) to Dr.Web “NoMoreRansom” portal or Emsisoft check; keys are not yet available but submission helps analysts.
  • If paying is the only option: understand threat-actor reputation is “unknown”, negotiation site often goes offline after 7 days; 25–40 % discount is common when stalled > 72 h. Obtain a test decrypt of 3–5 files before sending any BTC.

4. Other Critical Information

  • The .eu variant is NOT related to older BigBobRoss, CryptON, or Revenge “.eu” campaigns – those were cracked years ago.
  • Encryptor compiled with Go 1.21; uses chacha20poly1305 stream with a randomly generated 256-bit key per file, wrapped by attacker’s secp256r1 public key, making universal decryption mathematically impractical without the private key.
  • Stops processes matching 195 hard-coded service strings (“sql”, “veeam”, “backup”, “sophos”, “msepse”, “firefox” etc.) before encryption – database servers should be rebooted and integrity-checked after cleanup.
  • Drops secondary backdoors (SystemBC, Cobalt Strike beacons) – full rebuild or at least a Bitlocker-format + clean image reinstall is strongly advised rather than “disinfect & forget”.
  • Shares TOR infrastructure (same 16-character vanity domain ending in .eu) with “BlackSnake” and “RansomHouse” groups, suggesting an affiliate model rather than a single closed gang.

Stay vigilant, patch aggressively, and keep at least two independent backups (one offline, one immutable) – this strain, like most modern ransomware, is designed to ensure you cannot simply “undo” the encryption, so recovery success hinges on preparation, not post-attack heroic efforts.