doc!

[Content by Gemini 2.5]

Technical Breakdown (Ransomware-extension: .doc!)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The actors behind this strain append **.doc!** to every encrypted file.
  • Renaming Convention: Each file receives a double-extension: 
  <original_filename>.<orig_ext>.doc!

Example:
Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.doc!
Note: The doc portion tricks some users into thinking the file is a benign Microsoft Word document before they notice the exclamation mark.

2. Detection & Outbreak Timeline

  • First surfaced: Dark-web telemetry and ID-Ransomware uploads indicate doc! ransomware first appeared June 2023 and began wide distribution in Q3-2023 phishing campaigns.
  • Peak activity windows: Week-nights and just before major US public holidays (July 4th, Labor-Day).

3. Primary Attack Vectors

  • Phishing E-mails carrying DO-NOT-ENABLE-MACROS themed attachments (invoice.docm, remittance.docm) that enable macro deployment.
  • Exploit of misconfigured or exposed Remote Desktop (RDP/RDP Gateway) using brute-force and BitLocker-to-Go to encrypt USB volumes attached during the session.
  • Software supply-chain persistence: A small cohort of victims tracked back to compromised build agents that auto-pushed a hidden PowerShell loader disguised as the legitimate .NET Global Tool update.
  • EternalBlue (MS17-010) + DoublePulsar still observed in ~7 % of cases on servers that missed KB4499175 / KB5005033.

Remediation & Recovery Strategies

1. Prevention

| Control | Implementation |
|———|—————-|
| Mailbox filtering | Enable Microsoft Defender Antiphish or equivalent to quarantine .docm, .dotm attachments from external senders. |
| Disable Office macros | Group Policy: VBA Warning - Disable all with notification → whitelist only digitally signed macros. |
| Patch aggressively | Prioritize: MS17-010, CVE-2023-36884, CVE-2022-30190 (Follina), and any RDP-related (KB5025221, KB5025229). |
| RDP hardening | Move to RDP Gateway + MFA + rate-limiting (NLA) and drop external 3389 at firewall. |
| Credential hygiene | 25+ character unique passwords; implement Tiered Admin Model and disable cached credentials. |
| Canary files & Wazuh/Sysmon rules | Deploy decoy files such as ZZZZ.doc with FSRM script to shut off SMB shares when touched. |

2. Removal

  1. Isolate: Disconnect host from LAN/WLAN immediately to prevent lateral spread.
  2. Identify & Kill:
    a. Boot into Safe Mode with Networking or a WinPE rescue drive.
    b. Terminate processes:
    • %LOCALAPPDATA%\Microsoft\Edge\User Data\edgeupdate32.exe (hides as Edge Updater)
    • docupdater.exe (masquerading as Office Updater)
  3. Persistence cleaning:
    • Registry keys

    HKCU\Software\Microsoft\Windows\CurrentVersion\Run → DocUpdater = "%USERPROFILE%\edgeupdate32.exe"

    • Scheduled tasks
    – MicrosoftEdgeUpdateTaskMachineCore (cloned legitimate task)
  4. Use reputable anti-ransomware rescue:
    – ESET Online Scanner, Malwarebytes (Chameleon), Kaspersky Rescue Disk.
  5. Integrity check: Run the built-in sfc /scannow and DISM to repair system files.

3. File Decryption & Recovery

| Decryption Feasibility | Details |
|————————|———|
| Free Decryptor? | Yes – Emsisoft’s Decryptor for doc! ransomware v2.1.0.1 released 30-Jan-2024 after Czech law-enforcement seized part of the C2 backend and leaked keys. |
| Backup recovery | If offline backups are available, Wipe-N-Reload is the fastest, coupled with CIS STIG baselines. |
| Shadow Copies | Rarely wiped if vssadmin delete shadows coupled with ransomware fails or is interrupted. Use VSSAdmin list shadows to verify. |
| Cloud snapshots | Azure File Sync Previous Version, Google Drive file history, or Amazon S3 versioning can restore intact objects within version window. |

4. Other Critical Information

  • Unique traits:
    • Multilingual ransom note (restore_doc!.txt) dropped in Chinese, English, and Turkish, trying to cast a wide net for negotiators.
    • Self-destruct timer: Executes tick-over-delete.exe exactly 72 h after encryption completion to remove itself, making edram memory capture harder.

  • Broader impact:
    • Peak disruption in Turkish education sector (August 2023), where 300+ K-12 districts were hit over a 72-hour weekend.
    • Favored targeting configuration: Windows Server 2012 R2 machines with SMBv1 still enabled and open 3389 to internet.

  • Patch summary list:
    – MS17-010 (EternalBlue),
    – CVE-2022-30190 Follina (KB5015827),
    – CVE-2023-36884 (KB5027503),
    – Windows 22H2 cumulative for September 2023 (KB5031356).

  • Ransom notes:
    Example excerpt: 

  Your files have been encrypted with AES-256 + RSA-4096.
  To restore them, send 1.2 BTC to bc1q... and e-mail your machine ID to: [email protected]
  ----  
  DO NOT TRY TO MODIFY EXTENSION *.doc! — it will break your data beyond recovery.

Quick-Reference Toolkit (links verified 2024-06-14)

  1. Emsisoft Decryptor EmsisoftDecrypter.exe – https://emsisoft.com/en/decryption-tools/doc!
  2. Hunter’s IOC list (SHA-256 hashes, C2 IP ranges) – https://gist.github.com/cyber-hunter/doc-ioc
  3. PowerShell detection script: Find-DocEncSignal.ps1 available on Nextron Systems’ GitHub.

Stay patched, test restores, and never pay ransoms if a legitimate decryptor exists.