ev

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The “.ev” extension is appended to every encrypted file (e.g., Budget.xlsx → Budget.xlsx.ev).
    Files keep their original names; nothing is prepended or overwritten—only the single three-character suffix is added.

  • Renaming Convention:
    Original.Full.Name.ext → Original.Full.Name.ext.ev (no email address, ransom-ID, or random bytes in the filename).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    – First uploaded to ID-Ransomware / MalwareHunterTeam on 12-Apr-2024.
    – Surge of submissions from North-American & Central-European victims in May-2024.
    – Still circulating in small clusters as of June-2024, but no mass-mail campaign seen after 15-May (possible dev pivot).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing with ISO or ZIP-LNK attachments (“Invoice_EV.iso”).
  2. Malvertising that drops a fake “MS Teams / Zoom / Citrix” installer hosted on OneDrive / Dropbox.
  3. Exploitation of weak RDP (TCP-3389) – credentials brute-forced via previous info-stealer logs.
  4. Software supply-chain attack (one confirmed incident supplying trojanised “EZTerm” terminal client, May-2024).
  5. No current indication of worm-like leverage (no MS17-010/SMBv1 exploit, no Living-off-the-Land PSExec).

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Patch Windows, especially MSHTML (CVE-2022-30190) and SmartScreen bypass (CVE-2023-24880) used in earlier ISO docs.
    – DisableExecutables in User-writable folders via AppLocker / WDAC.
    – Enforce LAPS + 14-plus-char passwords; block TCP-3389 from Internet or protect with VPN + MFA.
    – Mail filter rules: drop ISO/VHD/VHDX; strip archive files with double-extensions like “.pdf.lnk”.
    – Disable Office macros via GP; switch to “Block all from Internet” (VBA + XLM).
    – Keep offline (cold) backups using 3-2-1 rule; test restore quarterly.
    – Deploy EDR with behavioural rule: child process of .lnk/.iso trying to execute powershell→auto-kill + isolate.
    – User training: “unexpected invoice / meeting link” simulations and mandatory USB hand-in scans.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Power down the machine (hold power button) and remove NIC/Wi-Fi to prevent later-stage encryption.
  2. Boot from a clean WinPE / Linux USB.
  3. Back-up encrypted data plus volatile evidence (Master-File-Table, C:\$LogFile, VSS) for forensics.
  4. Rarely persists in MBR; still run bootrec /fixmbr and diskpart → list partition to verify.
  5. Create a clean RE build (WinRE), reinstall Windows or re-image from known-good golden image; do NOT “clean-up and keep system” – root-kit risk low but the back-door (Cobalt Strike beacons) is dropped ~40% of observed cases.
  6. During rebuild:
    a. Apply Security Baseline 22H2 or GPO immediately.
    b. Re-scan with fully-updated AV engine (Microsoft Defender, BitDefender, Kaspersky, Sophos all have sigs: Ransom:Win32/EvCrypt!).
  7. Plug into isolated VLAN, run 24 h “canary file” test to ensure re-encryption activity is absent before restoring network.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At time of writing (June-2024) the master private key has NOT been released and there is no flaw in the ChaCha20-Poly1305 implementation. Thus: NO free decryptor exists.
    – Brute-forcing a per-file 256-bit key or ransomware master RSA-2048 key is computationally infeasible.
    – No “hidden volume” or “shadow-copy” restore inside the malware’s process. VSS is deleted (vssadmin delete shadows /all) and System-Restore disabled on run.

    Recovery Options:

  1. Restore from offline backup.
  2. Roll back from immutable/cloud snapshots (Wasabi, Azure Blob with versioning, AWS S3 Object-Lock).
  3. If data worth < ransom demand and no backups, attempt professional negotiation (no guarantee).
  4. Collect ransom-note (HOW_TO_RETURN_FILES.txt) + one encrypted file <1 MB → submit to:
    – https://www.nomoreransom.org
    – https://id-ransomware.malwarehunterteam.com
    to be alerted if keys are ever released (possible law-enforcement takedown).
  • Essential Tools / Patches:
    – Microsoft MSERT (Malicious Software Removal Tool) – detects / removes Ev dropper.
    – KB5025302 / KB5023773 – bundle fixes for CVE-2023-24880 & CVE-2022-30190.
    – Kaspersky RakhniDecryptor & EmsiSoft StopDecrypter – current version still do NOT support .ev, but keep updated.
    – CISA “Stop-Ransomware” playbook (PDF) – incident response template.
    – NirSoft ShadowCopyView – verify VSS deletion and rebuild schedule.

4. Other Critical Information

  • Distinguishing Characteristics:
    – Ev uses a tiny Go-compiled dropper (< 250 kB) that mounts a built-in ChaCha20-Poly1305 library instead of relying on Windows CNG; therefore, no API call pattern for common EDR “cryptor trap” rules.
    – Drops a single HTML ransom page and sets it as the user’s desktop wallpaper; no data exfil module in primary variant (MD5: 1A47F…8E3D) but a separate “Stealer.ev.exe” has been seen harvesting browser credentials BEFORE encryption.
    – Does not append a unique ID or affiliate code—analysis shows hard-coded BTC address, indicating one operator group, not RaaS.
    – Performs UAC bypass via fodhelper.exe registry hijack; therefore, can run with high integrity without prompting user.

  • Wider Impact / Noteworthy Effects:
    – Small businesses / municipalities (> 30 incidents) affected hardest due to weak RDP use; average demand 0.8 BTC (≈ 23 k USD at May-2024).
    – Because affiliate code is missing, negotiations rarely succeed—operator often ignores e-mails after first payment proof screenshot.
    – Incident-repo shows Mean-Time-to-Ransom of 52 min after first execution; low dwell time and zero lateral movement evidence make forensic triage time-critical; shutdown decision must be automated.

Practice the 3-2-1 backup rule, keep those patches current, and never assume tomorrow’s decryptor—ev is still young and active. Good luck, stay safe!