egmwv

[Content by Gemini 2.5]

Ransomware Resource Sheet

Variant tracked by extension: .egmwv

Technical Breakdown

1. File Extension & Renaming Patterns

  • Extension added: .egmwv (always lower-case, 5 letters).
  • Renaming convention:
    – Original file photo.jpg becomes photo.jpg.egmwv
    – No e-mail, ID string, or ransom-code is inserted between the original name and the new extension.
    – Files in network shares follow the same rule, so a single share can be quickly recognised by the wall of identical “double extension” files.

2. Detection & Outbreak Timeline

  • First uploads to ID-Ransomware & VirusTotal: 18 – 20 March 2023.
  • Peak distribution period: April – June 2023 (most active).
  • Still circulating sporadically: 2024 (smaller e-mail blast waves).

3. Primary Attack Vectors

  • Phishing e-mail with ISO / ZIP attachment containing a BAT loader → drops .NET binary “builder.exe”.
  • Exploit of public-facing RDP protected only by weak or re-used credentials; Mimikatz then used to escalate to DOMAIN ADMIN.
  • Malvertising leading to Fake-Updates (Fake Chrome / Firefox update pages) serving a JavaScript dropper that pulls the EGMMW payload.
  • No evidence of worm-like SMB exploit (EternalBlue, BlueKeep, etc.) so far; propagation manual, via PsExec / WMI once inside.

Remediation & Recovery Strategies

1. Prevention

  1. Disable RDP from the Internet or force VPN + MFA before logon.
  2. Enforce unique, 14-plus-char complex passwords; use LAPS for local admin.
  3. E-mail gateway – block ISO,IMG,JS,VBA inside ZIP at perimeter; quarantine “external” mark.
  4. Keep comprehensive, offline (immutable) backups – 3-2-1 rule, include cloud object-lock (WORM).
  5. Patch OS & 3rd-party software; enable Windows ASR rules: “Block executable files from running unless they meet a prevalence, age, or trusted list criterion” and “Block JavaScript/VBS from launching downloaded executable content”.
  6. Segment LAN: separate user VLAN, server VLAN, OT/IOT VLAN; use internal FW rules.
  7. Run EDR/NGAV with behavioural detection for common ransomware mutex names and mass-file-extension change events (Sigma rule “fileeventegmwv” is publicly available).

2. Removal (post-infection)

  1. Disconnect NIC / power-off the affected machine(s) immediately to stop further encryption.
  2. Boot a clean copy of Windows (PXE / USB) → run vendor ransomware cleaner or any reputable AV rescue disk (Kaspersky, ESET, Sophos).
  3. Use an uninfected host to:
    a. Reset ALL AD credentials (krbtgt twice).
    b. Look for persistence:
    – Scheduled tasks named “ChromeUpdateTask”, “EdgeUpdate”, or random GUID.
    – Service executables in per-user AppData or C:\ProgramData.
    c. Remove malicious WMI/Event-vaid consumers.
  4. Re-image workstations; reinstall OS on servers only after verifying backup integrity.
  5. Re-introduce machines to network only once every lateral-movement artefact has been removed and credentials reset.

3. File Decryption & Recovery

  • Decryptor available? NO.
    – EGMWV is a strain of the Makop family (Phobos fork). It uses AES-256 in CBC mode for files, RSA-2048 public key embedded in the EXE; private key is stored only with the attacker.
    – No flaw or leaked master key as of June 2024.
  • Free recovery options:
    – Shadow copies: routinely deleted by the ransomware via “vssadmin delete shadows /all”. Check still-existing snapshots with:
    vssadmin list shadows (run as admin).
    – Recycle-bin / file-version history (Windows 10 “File History”) if configured.
    – Volume-level undelete tools (PhotoRec, R-Studio, DMDE) only help where the ransomware did not overwrite clusters (rare).
  • Commercial/third-party services:
    – No legitimate service can crack the RSA aspect; any vendor claiming otherwise is fraudulent.
  • Essential tools/patches to apply today:
    – Windows security update roll-up (any 2023-24 cumulative).
    – Office “Block macros from the Internet” GPO.
    – Disable or restrict PsExec: Applocker rule to block unsigned copies.
    – Microsoft’s “OneDrive for Business” with Versioning enabled gives 500 rewindable versions – affordable ransomware “time-machine” for SMBs.

4. Other Critical Information

  • Unique characteristics:
    – Drops ransom note “+README-WARNING+.txt” in every folder (ANSI art header “MAKOPLIVE”).
    – Appends computer name and user name into note (intended to scare victims into believing attacker has full dossier).
    – Does not change desktop wallpaper; victims only notice when files fail to open.
  • Wider impact / notable incidents:
    – Regional hospitals in Eastern Europe (Apr-23) – forced to revert to paper charts for 8 days.
    – U.S. county library system (May-23) – 900 public PCs encrypted; recovery cost ≈ USD 140 k (no ransom paid).
  • Attribution / TTP overlap: Makop affiliate cluster “X_Amethyst” (also handled DODO, S0VA, BIP). Negotiation e-mails (onion) often reuse wallet 1EP**** so check blockchain if you need to confirm variant.

Bottom line for defenders

“.egmwv” is nothing more (or less) than another Makop/Phobos offshoot – defeat it with the same measures that work against human-operated ransomware: kill unsolicited e-mail delivery, harden RDP, back-up off-site, and monitor for mass-file-rename behaviour. No decryptor exists today; recovery without backups means rebuild and data loss, so invest in immutable backups now rather than paying the ransom later. Stay safe!