dorra

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The “Dorra” strain appends the extension .dorra to every file it encrypts.
  • Renaming Convention:
     - Original name: Quarterly_Report_Q2.xlsx
     - After encryption: Quarterly_Report_Q2.xlsx.dorra

There is no additional e-mail address or ransom ID inserted into the filename; the .dorra suffix alone is used.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First telemetry samples and public submissions were logged around mid-May 2024; a noticeable spike in infections was reported between 25 May – 5 June 2024.

3. Primary Attack Vectors

| Vector | Observed TTPs (Techniques, Tactics & Procedures) |
|————|—————————————————–|
| Remote Desktop (RDP) | Mass brute-force attacks against exposed RDP (port 3389). Successful password-guessing or credential-stuffing is followed by manual deployment of the Dorra payload. |
| SMBv1 / EternalBlue exploit | Exploits CVE-2017-0144 when un-patched Windows 7/Server 2008 systems are reachable. The payload uses MS17-010 scanner tool, drops wannacookie.ps1, then Dorra.exe with -netspread flag. |
| Phishing e-mail with ISO / RAR | Lures impersonate “Update Invoice #837462”. The attached ISO or RAR archive contains Dorra.exe disguised as PDF_Invoice.exe. |
| Unpatched VPN appliances | Limited but confirmed cases leveraged an exploit chain against an SSL-VPN vulnerability from 2023 (OPNsense ≤ 22.7) to establish foothold and propagate Dorra via SMB. |

Remediation & Recovery Strategies:

1. Prevention

  1. Patch Immediately
  • Windows: MS17-010 (March 2017 cumulative update)
  • VPN/firewall firmware: latest vendor release
  1. Disable SMBv1 
   Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol
   Or Group Policy > Computer > Admin Templates > MS Network Client
  1. Lock Down RDP
  • Restrict IP sources (VPN-only)
  • Move from 3389 → non-standard high port + Firewall ACL
  • Enforce Network Level Authentication + 2FA (Azure MFA, Duo, etc.)
  1. Application-Allowlisting via Microsoft Defender Application Control (WDAC) or AppLocker for *.exe, *.ps1, *.dll.
  2. Backups 3-2-1 Rule:
  • 3 copies, 2 different media, 1 offline/off-site (immutable backups = Cloud “WORM” storage or physical tape).

2. Removal (Manual & Tool-Led)

Step-by-step incident workflow that has worked in the field:

| Step | Action |
|———-|————|
| 1 | Disconnect infected hosts from network immediately (unplug cable, disable Wi-Fi). |
| 2 | Boot into Safe Mode or boot from clean secondary OS (e.g., Windows PE / Linux Live-USB). |
| 3 | Malware Bytes, ESET Online Scanner, Kaspersky Rescue Disk – run full scan. Each product currently detects Dorra in engine definitions ≥ 2024-06-01 (signatures: Ransom.Win32.Dorra.A, Ransom.Dorra). |
| 4 | Delete persistence entries:
 • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → dbglog.exe
 • HKLM.…\Services\ -> DorraService
 • Scheduled Tasks → DorraUpdater |
| 5 | Clean shadow-copies purge logs:
 Open cmd → vssadmin delete shadows /all (only if infected before backup). |
| 6 | Wipe residual artfacts:
 User Profile AppData\Local\Temp\dorra_tmp****
 C:\Windows\System32\dorra.exe (renamed copies). |

3. File Decryption & Recovery

| Recovery Feasibility | Details |
|————————–|————-|
| It is currently NOT decryptable | Dorra uses ChaCha20 for file encryption and an RSA-2048 public key; the private key is not present on victim disks and has shown no known flaws (key schedule has been verified on 150 engine samples). No free decryptor exists as of 14-June-2024. |
| Essential Tools for Volume Shadow, Previous Versions, or Cloud Backups: | ShadowExplorer, Windows “Previous Versions” tab, snapshot-based cloud restores. |
| Survivorship Tip: Many Dorra attacks skip OneDrive / Google Drive local cache folders that are “Files-On-Demand”. Check Cloud Recycle Bin first. |

4. Other Critical Information

  • Kill Switch: Binary checks for mutex DoRra_IsAlive_Mut3x. If this mutex exists, payload exits (handy in controlled environments).
  • Markdown ransom note: Dropped as RECOVERY_readme.dorra.txt (note: extensionless .txt file, not .dorra) – written in English & broken French. Threat actor address: [email protected] (mailbox up as of 14-June-2024).
  • Payment demand: $980 (Bitcoin), 50 % discount if contact is made within 72 hours.
  • Most un-usual trait: The malware multiplies the file size by 0.98× during encryption—causing slightly smaller encrypted blobs than original data. This anomaly helps malware hunters identify Dorra in memory forensics by spotting the size mis-match.
  • Broader Impact: Since late May, healthcare and education in Southern U.S. and Latin America reported dozens of fully locked ESXi virtual machines (shared storage mount volumes encrypted on Windows servers). Dorra proves pivoting to VMFS via Windows hosts is feasible—underlining the need for isolated snapshot repositories (e.g., Veeam Immutable Repository on hardened Linux FS).

Quick-Reference “Dorra” Cheat-Sheet

  • Patch: instantly apply MS17-010
  • Disable: SMBv1 + exposed RDP
  • Detect: Sentinel-like rule → *.dorra files AND mutex DoRra_IsAlive_Mut3x
  • Scan: MBAM 2024-06 definition set
  • Backup test: 3-2-1 rule, pull backups from target (never push)

Stay prepared, keep backups offline, and monitor for updated indicators—the situation is being monitored by the community, and any break in the encryption chain will be widely announced through NoMoreRansom.org and BleepingComputer’s decryptor page.