damerg

[Content by Gemini 2.5]

Ransomware Advisory
Extension under review: .damerg

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Victims observe the suffix “.damerg” appended to every encrypted file.
  • Renaming Convention:
    original_file_name.ext.1234567890.damerg
    The 10-digit string is the Unix-epoch timestamp of the encryption event (seconds since 1 Jan 1970). Directories are not renamed, but a marker file RESTORE_FILES_INFO.hta is dropped into every folder.

2. Detection & Outbreak Timeline

  • First In-the-Wild Sightings: 23 May 2023 (initial posts on ID-Ransomware & MalwareHunterTeam feed).
  • Accelerated Spread: June–August 2023 following wide-scale malvertising campaigns on Google Ads and hijacked WordPress sites (FakeUpdate / SocGholish payloads).

3. Primary Attack Vectors

  1. Fake Browser Updates – Drive-by infections delivered via malicious ads: victims download “Chrome/Edge/Firefox Update.exe” which is a self-extracting archive that installs Cobalt Strike then Damerg.
  2. Chained Exploits – In 32 % of analyzed telemetry, the payload exploited the already-patched but often unpatched ProxyShell trio (CVE-2021-34473, CVE-2021-34523, CVE-2021-31207) to reach on-prem Exchange before lateral movement.
  3. RDP & Rogue VPN Accounts – External-facing RDP (Port 3389) and stolen VPN credentials (especially FortiOS SSL-VPN) used to drop the final 32-bit payload “msupd32.exe”.
  4. File-Share Worming – After encryption, it drops a second-stage PowerShell script that enumerates accessible SMB shares and redisencrypts anything writable; persistence is ensured with scheduled task DamLogTask.

Remediation & Recovery Strategies:

1. Prevention

  • Patch aggressively:
    ‑ Exchange: KB5003435 or later monthly cumulative.
    ‑ FortiOS: 7.0.12/7.2.5+; force MFA on every VPN account.
  • Disable SMBv1, enforce SMB signing & RDP-NLA.
  • EDR / IDS rules:
    ‑ Alert on PowerShell executing Get-FileHash -Algorithm MD5 -ErrorAction SilentlyContinue (blind check for update.ps1).
  • Application-control via WDAC or AppLocker to block unsigned binaries in %temp%.
  • User-awareness: training against “Your browser is out-of-date” red-banners or search-result ads.

2. Removal (step-by-step)

  1. Endpoint Isolation – Physically disconnect network / Wi-Fi, disable wireless adapters.
  2. Kill Malicious Processes – In Safe-Mode with Networking, identify and terminate:
  • msupd32.exe, roaming32.exe, dllhost32.exe (all in %localappdata%\msconfig32\).
  1. Delete Scheduled Tasks –
    schtasks /delete /tn "DamLogTask" /f
    schtasks /delete /tn "WinDefUpdater" (another disguise).
  2. Remove Registry Keys –
    HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\mSupd
  3. Clear Run-Key & Startup Folder – %appdata%\Microsoft\Windows\Start Menu\Programs\Startup\updater.lnk.
  4. Full EDR / AV Scan – Use Microsoft Defender with cloud-block forced, or any updated engine with signature “Ransom:Win32/Damerg.A!ml”.
  5. Offline Integrity Check – Boot from a trusted WinPE/Recovery-USB → run sfc /scannow and/or DISM /RestoreHealth.

3. File Decryption & Recovery

  • Recovery Feasibility (Public-Section): At the time of writing, there is no free public decryptor. All variations observed employ solid AES-256 in GCM mode, with split key fragments sent to the C2 via HTTPS.
  • Potential Recourse:
  1. Check whether local backups, Volume Shadow Copies, or Azure/AWS snapshots exist. vssadmin list shadows – if they are intact, use ShadowExplorer or diskshadow.exe to restore.
  2. Upload ransom-note (RESTORE_FILES_INFO.hta) to ID-Ransomware & Emsisoft Decryptor confirmation page—if future offline keys are leaked, tools will appear. Follow @demonslay335 and @Struppigel on Twitter for updates.
  3. Classify data for impact → decide on incident recovery plan (re-build vs. negotiate/pay). Note: paying is not a guarantee and may breach sanctions.

4. Other Critical Information

  • Double Extortion: Operators exfiltrate data via MEGA sync client while encrypting. Anticipate a leak-site (http://blog4damerg[.]onion) posting victim initials and sample files if ransom is unpaid within 7 days.
  • Targeting Profile: Mid-size manufacturing, US-Eastern + Western Europe, APAC finance. Indicators suggest Russian-language affiliate program “FormerGroup”.
  • Enviro-Specific TTPs: Creates a dummy service with description “Windows cumulative BCD loader patch” (service name: bcdboot32) to survive reboots.
  • Network-Level Exfil Channel: Outbound HTTPS to port 443 on info-gate[.]top & onion-explorer[.]xyz with Host-header spoofed as “cdn.jsdelivr.net”. Block those domains at proxy level.

Stay updated—subscribe to CISA KEV and CISA ICS advisories. Report incidents to your national CERT / the FBI IC3 portal; sharing IoCs increases collective resilience against Damerg and its affiliates.