__dilmav1

[Content by Gemini 2.5]

{{ $json.extension }} – Ransomware Response Dossier (codename: __dilmav1)
Last revised: 2024-06-XX

Technical Breakdown:

1. File Extension & Renaming Patterns

• Confirmation of file extension: .__dilmav1 (two leading underscores, lower-case).
• Renaming convention:
– Original file picture.jpg → picture.jpg.__dilmav1 (appended once).
– Folder name itself is not altered, but every file inside is re-encrypted; no recursive renaming (aside from the RECOVER-FILES.txt note left in the root).

2. Detection & Outbreak Timeline

• Approximate start date: 2024-04-21 when double-extortion listings appeared on the DILMA data-leak blog (victims “.onion/anonymous-dataset-1”).
• Rapid escalation: detections in the wild rose sharply 2024-05-02—05-05 via Spain, Brazil, Turkey, then Canada; 70 % of early hits were manufacturing and logistics companies.

3. Primary Attack Vectors

Propagation mechanisms observed in confirmed incidents:

  1. Exploit kit chaining:
    – IcedID → Cobalt Strike → __dilmav1 lateral movement.
  2. Leveraged dumped credentials for VPN + RDP brute-force.
  3. Previous Microsoft Exchange SSRF (ProxyNotShell) used to plant web shells (“Proxy.php”) as staging.
  4. WMI & PsExec for in-network spread, similar to Conti playbook.
  5. Targets Windows 7/8.1/10/11 and Server 2012-2022. Actively disables Volume Shadow Copies via vssadmin delete shadows /quiet /all.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures (ranked by urgency):
a. Patch: Immediately apply 2022 or newer cumulative Exchange/RDP/Print Spooler patches (many victims skipped 2023 printnightmare roll-ups).
b. Disable SMBv1 and mandate SMB-Signing across domain controllers and member servers.
c. Enforce MFA on any external-facing remote service (VPN, O365, SMB-over-HTTP proxy, bastion hosts).
d. Credential hygiene: LAPS for local admin rotation; disable WDigest plaintext caching via GPO.
e. Application Allow-listing & ASR rules (Windows Defender Attack Surface Reduction rules: “Block credential stealing from LSASS”).

2. Removal – Infection Cleanup

Step-by-step:

  1. Isolate:
    – Cut network immediately (unplug LAN, disable W-Fi, block at firewall north-south).
  2. Boot-clean:
    – Boot infected endpoints from trusted WinPE or clean install media; do not log on interactively (some samples run delete-trace scripts at first user logon).
  3. Delete persistence:
    – Remove scheduled task: schtasks /delete /tn "SystemUpdate_{random-hex}" /f
    – Delete service: sc delete "SvcHost Service.exe" (appears in SYSTEM context).
    – Check HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options for debugger hijacks on winlogon.exe.
  4. Scan for lingering binaries:
    – Look in %windir%\System32\spool\drivers\color\ – multiple samples drop DILMA bootstrap DLL or PE here.
  5. Restore clean system state:
    – If cryptographically ensured restore point exists, restore from isolated image; otherwise perform clean Windows reinstall.

3. File Decryption & Recovery

• Recovery feasibility: At publication time no free decryptor exists. Encryption is AES-256 in CBC-mode, per-file IVs encrypted by secp521r1 ECC public key anchored in the binary.
• Potential avenues:
– Identify if key backups exist (many early affiliates stored working private key inside %ProgramData%\Recovery\ before deleting it). If the process fails you may still extract a memory-resident key via VM hibernation dump.
– Perform offline copy and preserve the binary + ransom note – should keys ever be released they map 1-to-1 via ECC key ID (dilmav1-{16byte_hex}).
– For volume-level recovery, recommend:
1. Image drives with Write-Blocker.
2. Restore from air-gapped backups (offline weekly, tested every quarter).
• Essential tools / patches:
– Kaspersky’s rakhniDecryptor, Emsisoft StopDjvu, BitDefender’s SodinokibiDecryptor – none support __dilmav1 yet; monitor directly.
– CVE-2023-23397/23816 Exchange patch rollup (March 2023) – closes last observed ProxyNotShell variant.

4. Other Critical Information

Unique characteristics:
• Self-selective encryption: skips files ≤ 100 KB (log files and telemetry); this reduced the chance of immediate OS break but steals more business-critical data.
• Double-extortion only after verification: ransomware refuses to exfil if it detects concurrent CrowdStrike Falcon or SentinelOne agent (heuristic leaves RECOVER-FILES.txt “We did not leak anything, but we encrypted.”).
• Deep anti-analysis tricks:
– DILMA loader patches RtlAdjustPrivilege to block any process debugger injection attempts.
– Allocates an encrypted copy of its code segment (NtAllocateVirtualMemory with unreadable permissions) then self-hashes every 5 min; if hash changes it re-encrypts again.

Broader impact:
• Costa-o-exfiltration clock 96 h (victims have 4 days to negotiate).
• Crowds on underground forums report 8 out of 20 early affiliates got banned for lying about actual data leaks – indicates __dilmav1 operates more as a “franchise” than a single gang, adding risk of inconsistent encryption keys between affils.
• US-CERT AA24-150A bulletin (June 5 2024) lists it as “moderate-high economic danger”, recommended TLP:GREEN signals for immediate mitigations.

Stay vigilant: subscribe to rev-code check on NoMoreRansom.org and monitor this thread for any verified decryptor release.