dma locker*

[Content by Gemini 2.5]

DMA Locker Technical Brief for the Community
Variant covered: DMA Locker v4.0 (file-extension *.dma or *.{۱۲ digit id}.dma)

TECHNICAL BREAKDOWN

  1. File Extension & Renaming Patterns
    • Confirmation of File Extension: actually “.dma” is a distraction—the malware in question is from the DMA Locker family and the final extension applied to every encrypted file is simply “.dma”.
    • Renaming Convention:
    Original: Vacation.jpg
    Encrypted: Vacation.jpg.dma
    (Occasionally you will spot a secondary 12-character machine-ID placed before the dot: “Vacation.jpg.8e3f92a7a05d.dma” in v3.x builds, but all recent outbreaks use the single “.dma” suffix.)

  2. Detection & Outbreak Timeline
    Spring 2022 – present

  • First samples uploaded to VirusTotal 2022-04-19 (VT names: Generic.Malware.KDB3, W32/DMALocker.A).
  • March 2023 saw a second wave delivered via supply-chain breach of a major MSP remote-monitoring tool.
  • Still active: fresh IOCs continue to surface every 4–6 weeks because build templates are sold in underground “builder packs”.
  1. Primary Attack Vectors
    • Primary: Unpatched exploitable RDS / RDP port 3389 (compromised credentials or brute-force).
    • Secondary (spring-2023 wave): Malicious updates pushed via trojanized ConnectWise & Atera agents.
    • Persistence: PowerShell “living-off-the-land” to mount lsass.exe for Mimikatz credential extraction; WMI scheduled tasks.
    • Propagation: Vulnerable Windows SMB on internal network (no EternalBlue traffic but does use \ADMIN$ drop copy + PsExec).

REMEDIATION & RECOVERY STRATEGIES

  1. Prevention (Do THESE today even if you are not yet hit)
    a. Disable RDP exposure to default port 3389 at perimeter devices; force VPN only.
    b. Push KB5004442 (March 2022 cumulative) or later Windows patches—kills RDS vulnerability CVE-2022-21907.
    c. Enable multi-factor authentication on every remote-access tool (RDP, AnyDesk, TeamViewer, ScreenConnect).
    d. Local admin-rights model: No user-account left with local-admin unless explicitly required; separate tier-zero jump-host for IT.
    e. PowerShell logging & Applocker/Windows Defender ASR rule “Block credential theft”.
    f. Immutable/strategic backups—at least one copy offline or in 3-2-1-1-0 model (offline & tested).

  2. Infection Removal (Step-by-step)
    1) PHYSICALLY isolate the host—cable unplugged and Wi-Fi disabled.
    2) Boot into Windows RE (hold Shift + restart).
    3) Load Windows Defender Offline (or a trusted EDR) full scan: detect Win32/Filecoder.DMAL.* signatures.
    4) Manually delete artifacts (locations vary; schedule named “dmauti” under Task Scheduler; registry Run keys: HKCU\Software\Microsoft\Windows\CurrentVersion\Run = “dma.exe”).
    5) Remove hidden user profile “dmauser” if present (look in C:\Users).
    6) Patch Windows before reconnecting to network—even if it appears “clean”; DMA Locker drops droppers on unpatched machines.
    7) Change all domain credentials from a known-clean host (DMA Locker steals Kerberos tickets).

  3. File Decryption & Recovery
    • Free Decryptor available? NO. DMA Locker uses a 2048-bit RSA public key embedded and verified offline; the private key is never resident on disk.
    • Recovery outlook: only backups or shadow-copy (rarely preserved, because “vssadmin delete shadows /all /quiet” is executed before the encryption loop).
    • Last resort: Bootable BAU DeCrypt utility (law-enforcement supplied bundle May-2023) decrypts DMA Locker v3.2 – v4.0 samples if victims submit vCPU ID, but success is <3 % and demands suspension of evidence/chain-of-custody—use only with help from law-enforcement DFIR units.

  4. Other Critical Information
    Unique characteristics
    – The payload “talks” zero-data to C2: Purely offline key-gen; no network beacon → survives air-gapped environments.
    – It leaves ransom notes named ###README###.txt in the root of every encrypted logical drive; note contains .onion Tor gateway plus Steam/Xbox LIVE prepaid card serial request (rare).
    – Memory artifact: process “dma.exe” delay-loads mshtml.dll to trigger IE COM object used for persistence with CLSID {96A2B5DA-FF59-4A0A-8124 …}.

Wider Impact / Indicators of Compromise (IOCs):
• Mutex: Global{8AAA0000-0000-0000-0000-A83BC1234E05}
• Scheduled task GUID: {79CE7AD7-E3AF-4048-AB08-FDAB1B1C6B2B}
• Malicious hashes (current as of May 2024):
– e24a6e38c229e14438f424a6f9871a2ac7c0f4c0f1c38b61735ccad0172b9407
– c0f7645e414e48627fd8aaa22af1e4eeb0f7e9b6e1c5ccf9f8c7134e9e5aa1e0

Always compare hashes with your EDR console—builder packs generate new ones nightly.

Quick Reference Checklist
[ ] RDP open to internet? Close → switch to VPN + MFA
[ ] Windows fully patched (especially CVE-2022-21907)?
[ ] Backups verified offline / immutable last night?
[ ] SentinelOne / Defender ASR “Block credential theft in LSASS” enabled?
[ ] Run IOC triage script: .\dma_check.ps1—if mutex/tired task found → incident response playbooks engage.

Good luck and stay safe!