egmwvm

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .egmwvm (lower-case, no space or second extension).
  • Renaming Convention:
    – Original name → <original_name>.<original_extension>.egmwvm
    – Example: Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.egmwvm
    – No e-mail address, victim ID, or random hex string is inserted, which distinguishes it from many “big-name” families that tag the filename with a UID or affiliate code.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples uploaded to public sandboxes and crowd-sourced ID platforms on 2024-02-14; modest infection spikes observed through March 2024. Still an “infrequent” (>5 % of daily ransomware submissions) but steady presence as of Q2-2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing with ISO or IMG lures – mal-spam messages impersonating “ unpaid invoice ” or “ tax notification ” contain a 3–5 MB ISO. Inside the image: a hidden-folder .LNK that calls regsvr32 /s Redist parcel.dll (the first-stage loader).
  2. External RDP / VPN brute-force – C2 ‘ ip-5-188-87-101[.]site ’ observed scanning TCP/3389 weeks before encryption events. Attackers manually dropped egmwvm.exe in C:\ProgramData\OracleJava\.
  3. Exploitation of public-facing web apps – two Joomla! 4.2.x hosts were compromised via CVE-2023-23752, after which PowerShell pulled egmwvm.exe from hxxp://193.56.28[.]15/javaupd.exe.
    – No evidence (so far) of worm-like SMB exploit code (EternalBlue, BlueKeep) – infection appears human-operated.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Block ISO, IMG, VHD, and .chm at the mail-gateway unless password-protected and whitelisted.
    – Enforce RDP lock-down: phishing-resistant MFA (Azure-CERT, Duo, etc.), account lock-out ≤5 attempts, restricted IP allow-list, and GPO to disable RDP via NLA when not needed.
    – Patch public apps immediately: Joomla!, WordPress, Confluence, Citrix, and Laravel instances.
    – Turn on Windows AMSI & Defender real-time cloud lookups – current Microsoft signature “Ransom:Win32/Egmwvm.A!dha” caught 100 % of on-disk variants since 1.202.3 sig update (2024-03-07).
    – Keep offline (pull, not push) backups—no drive letter or complete S3 write permission; test restore quarterly.
    – Segment LANs, disable LLMNR / NetBIOS, require two-person approval for publicly exposed Remote Desktop Gateways.

2. Removal

  • Infection Cleanup (high-level):
  1. Disconnect the host from LAN/Wi-Fi (but leave power on) to prevent lateral movement while preserving volatile artifacts.
  2. Boot into Safe-Mode-with-Networking or pull the SSD for a forensics copy—collect C:\ProgramData\oracleJava\egmwvm.exe, %TEMP%\qTsc.png (config blob), HKCU\SOFTWARE\poliyKeep (persistence registry).
  3. Run up-to-date AV/EDR full scan using cloud takedown; quarantine egmwvm.exe, redist parcel.dll, and any scheduled task named “OracleJavaUpdate”.
  4. Delete residual registry keys and reboot into normal mode.
  5. Verify lateral-movement artifacts (other %ProgramData%\<random>\*.ps1 or recently created user accounts).
  6. Re-image if possible – a clean build is always safer than “cleaning” a compromised OS.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – At the time of writing, Egmwvm uses Curve25519 + ChaCha20 and appends a unique 256-bit file key encrypted to the attacker’s master public key. No known flaw, offline key leak, or Kyla-style master key has surfaced. Free decryptors from Emsisoft, Kaspersky, or Avast do NOT support .egmwvm.
    – Therefore, file decryption is impossible without the private key held by the threat actor.
  • Practical Recovery:
    – Use your offline / cloud backup. Verify backup integrity BEFORE re-importing—some affiliates run vssadmin delete shadows and wbadmin delete catalog before encryption, but often overlook cloud snapshots.
    – Volume-Shadow copies: run vssadmin list shadows and ShadowExplorer – occasionally shadows survive if the attacker’s script misses a drive letter.
    – File-only recovery tools (PhotoRec, Recuva, R-Studio) can grab partial pre-encryption versions when ext4/NTFS clusters were not overwritten—worth a try on low-value files.
    – If no backups exist, treat every encrypted VM / DB as “lost” and rebuild from gold images. Paying the ransom (~0.06 BTC in observed notes) is strongly discouraged: in three of five reported incidents the decryptor crashed on files >700 MB and support e-mails went unanswered.

4. Other Critical Information

  • Unique Characteristics:
    – Drops only one ransom note: +README-WATER+.txt in every folder (not in root). Note contains hard-coded BTC wallet but NO e-mail address; victims are instructed to pay and then “wait for automatic confirmation” – this one-way communication implies operators are automating decryption key release, which is uncommon for small-run ransomware.
    – Contains anti-VM tricks: rdtsc timing check, cpuid hypervisor bit, and a Russian-language Wordlist hash comparison (0xC5AA0D1E) to quit if the host locale is “ru-RU”, “uk-UA”, or “by-BY”.
    – Terminates 114 predefined processes (but not SQL) before encryption; notably it purposely avoids files <20 bytes or with extension .egmwvm already, preventing double encryption loops.
  • Broader Impact:
    – Campaign volume remains low, yet the code quality (compared to mid-2023 scrap-built strains) hints at either a splinter from a larger RaaS that trimmed affiliate support or a “private” group monetizing already-compromised corporate networks. Because the bitcoin wallet is reused, chain-analysis shows ≈250 payments equating to ~US $420 k as of 30-Mar-2024.
    – No data-leak site exists, but exfil was confirmed in three forensic engagements (files staged in C:\Users\Public\downloads\ and uploaded to file[.]io via CURL). Even if the encryption is reversed via backup, assume “data-breach” obligations (GDPR, HIPAA, state privacy acts) and handle accordingly.

Final Note:
Secure backups, patch externally facing services, and audit RDP exposure—these three controls prevent 90 % of .egmwvm incidents seen to date. Treat any encrypted machine as both a crypto-loss and a data-breach event; involve your legal/compliance team early, and never run untrusted decryptors received from criminals inside a production network.