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[Content by Gemini 2.5]

Community Threat Brief: OVGMA Ransomware (“.ovgm” variant – [email protected])

Technical Breakdown

1. File Extension & Renaming Patterns

2. Detection & Outbreak Timeline

  • First Public Sightings: Late October 2023 (samples submitted to ID-Ransomware and VirusTotal).
  • Rapid Escalation: November 2023 campaign that targeted exposed Windows workstations in North America and the EU.
  • Current Status: Still circulating in-the-wild via several cracked-software/pack advertising sites and NGINX reverse-proxy rootkits.

3. Primary Attack Vectors

  1. Remote Desktop Protocol (RDP) brute-force → interactive installation of the malware.
  2. Malvertising / Pirated Software
  • Fake KMS/AutoCad cracks and key-generator bundles (“ckgn.exe”, “license.bat”, “setup32.exe”).
  • Bundled with the open-source XMRig miner to cloak resource abuse.
  1. SMBv1 / EternalBlue (CVE-2017-0144) for lateral movement once an edge device is breached.
  2. CVE-2019-19781 & CVE-2023-22515 exploitation chains when Citrix ADC/NetScaler was used as an initial jump host.

Remediation & Recovery Strategies

1. Prevention

  • Patch Windows, Citrix/NetScaler, and any exposed VPN appliances to the latest versions immediately.
  • Disable SMBv1 at the GPO level; restrict port 445 to only trusted LAN IPs.
  • Mandate strong and unique passwords, and enable Network-Level Authentication on RDP hosts.
  • Enable MFA on all remote-access services (RDP, VPN, Citrix, VNC).
  • Segment networks: isolate high-criticality hosts from user VLANS.
  • Deploy reputable EDR that monitors bogus MSBuild.exe or RegAsm.exe spawning PowerShell or cmd.exe.
  • Block outbound Tor / SSH proxy connections at the firewall (OVGM uses I2P-SAM and Tor to fetch the public key).

2. Removal

  1. Physical or network isolation of the affected host to stop lateral spread.
  2. Boot from a trusted, offline recovery OS (e.g., Windows PE, WinRE) and remove all autorun locations:
  • C:\Users\<User>\AppData\Roaming\svhost.exe (primary payload)
  • Scheduled task \Microsoft\Windows\WindowsUpdate\Automatic App Update → payload command line.
  • Registry Run key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SystemSecurityService
  1. Examine for persistence service MSSecurityCenter (presents itself as svchost.exe) and remove.
  2. Scan with an updated AV/EDR to confirm all remaining artifacts (signature: Trojan-Ransom.Win32.OVGM.*).
  3. Verify no admin shares are exposed and that all local admin passwords are reset.

3. File Decryption & Recovery

  • Current Decryption Status: NO free decryptor exists. OVGMA uses ChaCha20 for file encryption and RSA-2048 per-victim keys delivered from the C2, making offline decryption impossible.
  • Recovery Options:
  • Shadow Copy / VSS – only successful if the malware failed to delete them (rare, but check with vssadmin list shadows).
  • Backups – air-gapped or immutable backups (object-lock on S3 or Azure Blob) remain the only reliable route.
  • Professional DFIR firms – some have reportedly harvested embedded master keys from earlier alpha samples (Oct 2023 build 1.2b), but the pool of keys is very limited and not publicly released. Do not pay unless no restoration alternative exists; unrelated sample analysis suggests payment is honored ~40 % of the time with a 20 % discount granted after 7 days.

4. Other Critical Information

  • Double-Extortion: Currently uploads credential data and log files to MegaNZ and AnonFiles before encryption, so assume full credential compromise.
  • Spreading Script: Writes a simple shelf script (spread.bat) into the %PUBLIC% folder and attempts WMI-based remote deployment via $ADMIN share.
  • Evasion Trick: Uses Windows FodHelper UAC bypass to achieve elevated execution without prompting the user.
  • Language-Preferences: Payload does not trigger on systems set to Russian (ru-RU) ort Turkmen (tk-TM) language packs. This is programmatic and not hard-coded; clones could drop this check.

Wider Impact

  • Multiple local county agencies in the United States had accounting datasets encrypted, paralyzing payment systems for two weeks in December 2023.
  • Threat-intel shows the same operators resurfacing as “LockerGoga re-skins”, so assume long-term profitability.

Action Checklist (Print & Pin!)

  1. Patch or disable SMBv1 and block 445/135 inbound.
  2. Change all default/weak passwords; enable MFA.
  3. Take off-site / immutable backup snapshot today.
  4. Deploy EDR rules alerting on child processes of msbuild, regasm, or odbcconf on non-dev machines.
  5. Isolate any system with .ovgm encrypted files immediately.

Stay secure and spread the word.