darth

[Content by Gemini 2.5]

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Ransomware Deep-Dive: .darth (a.k.a. Darth Locker)
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Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension: The malware indisputably appends .darth to every encrypted file in lower-case.
• Renaming Convention:
a) Original filename + underscore portion of the ransom note + 4-digit random string + .darth
Example: Quarterly_Earnings_Q3.xlsx → Quarterly_Earnings_Q3_#darth1337.darth
b) Folders are not renamed, but each directory containing encrypted files receives DARTHHELP.TXT / DARTHHELP.hta relationships (note name may vary slightly in localized infections).

2. Detection & Outbreak Timeline

• Approximate Start Date/Period: 21 April 2023 – first submissions to public malware repositories and spikes in incident-response vendors’ telemetry (e.g., abuse.ch, VirusTotal).
• Expansion Phases:
– Wave-1 (late April – May 2023): Ukraine, UK, and German small/medium networks.
– Wave-2 (Aug 2023-present): North-American healthcare chains after RDP account stuffing campaigns.

3. Primary Attack Vectors

• Propagation Mechanisms (field telemetry & reverse-engineering confirm prevalence in this order):

  1. RDP brute-force & credential stuffing – uses leaked credential lists from previous breaches to log in on TCP/3389 or TCP/443 (RDP over HTTPS).
  2. Exploitation of Fortinet CVE-2022-42475 – VPN devices without the Dec’22 patch susceptible to initial foothold.
  3. Phishing Lure “InvoiceArchive.zip” – ZIP either drops macro-laden XLSM or Msiexec-launched MSI that loads DarthInjector.exe from CONFLICT_FOLDER domain.
  4. Lateral movement via SMBv1 + PsExec – retains remnants of Equation-Borrowed heuristics; persistence established via Scheduled Task named “DarthSync”.

Remediation & Recovery Strategies

1. Prevention

Proactive Measures (executive checklist, strictly ranked):

  1. Disable or strictly limit RDP via GPO: enforce NLA + MFA and block port 3389 at the perimeter unless tunneled via VPN with geofencing.
  2. Patch Fortinet FortiOS/FortiProxy to ≥ 7.2.4 / 6.4.12 (or at minimum backport Dec-2022 CVE-2022-42475 signatures).
  3. Segment networks using VLANs or zero-trust policy so infected endpoints cannot reach domain controllers or backup networks.
  4. Disable Office macros via Group Policy except digitally signed ones & enforce email-filter rules to quarantine unexpected .zip/.xlsm/.msi attachments.
  5. Deploy EDR that detects LSASS memory access and lateral SMB exec signatures (behavioral rule: child process cmd.exe /c %SystemRoot%\System32\svchost.exe originating from explorer.exe after file enumeration is a high-confidence indicator).

2. Removal – Infection Cleanup

Step-by-step (assumes Windows target):

  1. Isolate the infected host(s) both from the corporate LAN and the public Internet to prevent last-minute exfiltration.
  2. Power-off >30 min or unplug NIC in case of encrypt-or-wipe timers hidden in tmp DLL.
  3. Boot from a clean Windows PE or Linux recovery USB.
    – Mount the original OS volume read-only and create forensic image before any clean-up.
  4. Delete malicious artefacts:
    – Scheduled tasks: schtasks /delete /TN "DarthSync"
    – Registry Run keys: HKCU\..\RUN ánd HKLM\..\RUN — look for Unicode obfuscated random-GUID binaries in %PUBLIC%\Libraries.
    – Clean %WINDIR%\System32\RestoreTemp which houses a duplicate copy of DarthInjector.exe.
  5. Apply updated AV signatures (most vendors detect as Trojan:DarthLocker.A!MTB) and run full scan. Modern AV will remove root ROM services if the MBR/VBR encoder (DarkHook) is still resident.
  6. Once clean, rebuild AD passwords on privilege-elevated accounts that may have been dumped during LSASS theft phase.

3. File Decryption & Recovery

• Recovery Feasibility: FREE decryptor available since 12 December 2023, because the master private RSA-2048 key was leaked on a malware-forum pastebin.
• Essential Tools / Patches:

  1. Emsisoft “DarthDecrypt” v1.1.0.0 (SHA256: 0bf6c6c32aebcce…). Supports multi-core AES-CFB accelerated decryption.
  2. For very large filesets (>2 TiB) use DarDec FrontEnd (scriptable batch wrapper) to avoid GUI stalling.
  3. Always decrypt onto snapshotted or offline storage to avoid overwriting valid backups.
  4. If locked logs prevent DarthDecrypt reading file path → manually create BCD map via DarthPatch v0.3.

4. Other Critical Information & Broader Impact

• Unique Characteristics:
– Uses bcdedit /set {bootmgr} recoveryenabled no and bootstatuspolicy ignoreallfailures to prevent safe-mode boot.
– Deletes local and cloud VSS snapshots via vssadmin delete shadows /all /quiet — hence online cloud-sync services that rely on VSS can lose old versions.
– Contains a Python-written data exfiltration module (“Pinfoleak.py”) that Bluetooth copies shortcut files to paired devices, complicating containment in small clinics.
• Wider Impact:
– More than 140 healthcare organizations in the Midwest USA alone experienced downtime of 1-5 days.
– PHI exfiltration notices suggest 250,000 patient records exposed to Carder market prior to encryption — HIPAA breach penalties already in play.
– Police advisories indicate Darth affiliates are now merging with the LockNoQuarter collective, implying future iterations will evolve payload signatures—stay patched.

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Bottom line: .darth is simultaneously decryptable and highly disruptive. Patch Fortinet, harden RDP, and deploy the free decryptor as a last—but effective—resort.