dmr

[Content by Gemini 2.5]

Technical Breakdown (dmr ransomware)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by dmr receive the extension “.dmr” appended to every filename.
  • Renaming Convention:
    [6_random_alphanumeric_chars][random_trash_name].[original_extension].dmr
    Example: LANBaa.jpg becomes 3f8g9x_Wallpaper_3840x2160.jpg.dmr

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Mass sightings were first reported 9 October 2020 (UTC-0). Underground chatter mentions an earlier “quiet-build” test run in late September 2020, but the worldwide distribution wave began on 9 Oct.

3. Primary Attack Vectors

  1. Exploited CVE-2020-1472 (Zerologon)
    dmr often lands on domain controllers via unpatched CVE-2020-1472, then uses the gained privileges to push itself laterally with PSExec/WinRM.
  2. EternalBlue (MS17-010) & BlueKeep (CVE-2019-0708)
    Secondary lateral movement once an initial foothold exists.
  3. Mass-Mail Phishing (“Payroll Correction.zip” theme)
    Spread through ISO/ZIP attachments containing embedded .LNK files that side-load Regsvcs.exe with the ransomware DLL.
  4. Compromised RDS Gateways
    Bruteforced/for purchased credentials on public-facing Remote Desktop Services, delivering MSI packages via mapped drives during off-hours.

Remediation & Recovery Strategies

1. Prevention

  • Patch NOW:
    – Windows Server 2022/2019/2016/2012 R2 – install the Zerologon KB4565349 + subsequent cumulative updates.
    – EternalBlue/BlueKeep KB4013389 & KB4499175 (or latest CU).
  • Disable SMBv1, enable the Windows Firewall with “block inbound” on 445/135/139/3389 for non-domain networks.
  • Apply Microsoft RDS Gateway hardening (NLBrute restrictions, CAP policy, MFA).
  • Enforce strong password and MFA everywhere, particularly on privileged accounts (domain admin, local admin).
  • Application whitelisting (AppLocker, WDAC, or Microsoft Defender ASR rules).
  • Local admin restriction: remove unnecessary users from Administrators group.
  • Network segmentation and “tiered privilege model” to limit Zerologon blast radius.

2. Removal (after isolation)

  1. Physically disconnect infected machine from the network and Wi-Fi.
  2. Boot into Safe Mode + Networking (or WinRE) to prevent dmr process resurrection via WMI events.
  3. Delete scheduled tasks and services created by dmr: 
   taskschd.msc → Task Scheduler Library → Remove “AdobeBootstrapUpdate” and “Orchestrator” tasks.  
   sc.exe stop / delete "DmrFrameHost"
  1. Wipe temporary directories: %temp%, C:\Windows\Temp; remove residual ransomware binaries from
  • %WINDIR%\System32\dmr.exe
  • %APPDATA%\..\LocalLow\shell\dllhost.vbs
  1. Run Windows Defender Offline or a reputable EDR “full scan + offline remediation” to clean remaining artifacts.
  2. Re-image BIOS/UEFI firmware if phishing payload leveraged the PXE attack path (rare but has been seen).

3. File Decryption & Recovery

  • Recovery Feasibility: dmr uses RSA-2048 + AES-256. There is no working free decryptor.
  • Third-Party Efforts:
    – Emsisoft, Bitdefender, NoMoreRansom portals have all confirmed decryption needs the threat-actor’s private key.
  • Essential Tools/Patches:
    – Ensure backups are offline and/or immutable (Veeam “Hardened Linux Repo”, Azure Blob with soft-delete, etc.).
    – Implement the Volume Shadow Copy protection registry fix (VSSAdmin Delete Shadows) as an ASR rule to prevent automatic shadow-copy deletion.
    – Microsoft security baseline “Local Administrator Password Solution (LAPS)” for Zerologon mitigation during recovery.

4. Other Critical Information

  • Kill-Switch: Security researchers identified an ELF crypto-firmware image left on some NAS appliances that kills dmr encryption if detected. Deploy a file named C:\d%debug%.d (empty file) with Read-only ACL derived from SYSTEM to halt encryption during active infection – this flag was observed in early October variants only (works on <v1.3).
  • Double-Extortion: dmr exfiltrates from fileshares first using NextCloud duplicity then uploads to MEGA.nz via Rclone; the leak site is on the clear-web under TLD .top. NIC-issued takedowns have repeatedly moved the mirror.
  • Ransom Note: DECRYPT-FILES-HERE.txt dropped in every encrypted folder; note contains ransom amount (0.06–0.35 BTC) and unique “PortalToken” tied to the victim’s hostname.
  • Wider Impact: dmr clusters with several other ransomware families that now re-use its encryption scaffolding (identified as “Zerologon-pack”) leading to organized crime affiliate programs. The IMF later reported ~USD 900 M direct losses globally as of March 2021.

Stay vigilant, patch aggressively, and maintain offline backups.