Remove STOP/DJVU Ransomware and Recover Encrypted Files

Symptoms

STOP/DJVU ransomware is a widespread file-encrypting malware that typically spreads via cracked software downloads, malicious email attachments, or fake update prompts. Common symptoms include:

• Files renamed with extensions like .djvu, .tro, .pdf, .docx followed by a random string (e.g., photo.jpg.id-123456.[random@email].djvu).
• A ransom note named _readme.txt or !!!READ_ME!!!.txt left on the desktop or in each affected folder.
• Inability to open documents, images, or databases.
• System slowdown and unusual network activity.

Root Causes

The infection occurs due to:

• Downloading and running cracked or pirated software (keygens, activators).
• Opening malicious email attachments or links (phishing).
• Clicking fake pop-up ads or update notifications.
• Exploiting outdated software or operating system vulnerabilities.

STOP/DJVU uses AES-256 encryption and appends a unique ID to each file. The offline key (when the malware cannot contact the C2 server) is sometimes recoverable, but the online key is unique per victim.

Step-by-Step Fix

Step 1: Isolate the Infected System

1. Disconnect the computer from the internet immediately (unplug Ethernet or disable Wi-Fi).
2. Do not reboot if possible; some variants may encrypt more files on restart.
3. Disconnect any external drives or network shares to prevent further encryption.

Step 2: Remove the Ransomware

1. Boot into Safe Mode with Networking (press F8 or Shift+Restart during boot).
2. Download and run a reputable anti-malware tool (e.g., Malwarebytes, HitmanPro, or Kaspersky Virus Removal Tool).
3. Perform a full system scan and quarantine/delete all detected threats.
4. Use a dedicated ransomware removal tool like Emsisoft Emergency Kit or Norton Power Eraser.

Step 3: Attempt File Decryption

1. Visit the Emsisoft STOP DJVU Decryptor website (https://www.emsisoft.com/ransomware-decryption-tools/stop-djvu).
2. Download the latest version of the decryption tool.
3. Run the tool as administrator and click Decrypt.
4. If the tool identifies an offline key, it will decrypt your files automatically.
5. If it fails, note the error message (e.g., "No key found"). You may need to upload a sample encrypted file and ransom note to the Emsisoft support team for analysis.

Step 4: Restore from Backup

1. If you have a clean backup (external drive, cloud, or NAS), ensure the backup is disconnected from the infected PC.
2. After removing the malware, restore files from backup.
3. Do not restore any files that were backed up after the infection date.

Alternative Fixes

• Shadow Volume Copies: Check if Volume Shadow Copies exist (right-click file > Properties > Previous Versions). Some STOP variants delete them, but it's worth a try.
• Professional Decryption Services: If the decryption tool fails, contact a reputable data recovery service (e.g., Emsisoft, Kaspersky, or local experts). Avoid paying ransom.
• File Repair: For specific file types (e.g., images, documents), specialized repair tools may recover partial data.

Prevention

• Regular Backups: Maintain 3-2-1 backup strategy (3 copies, 2 media, 1 offsite). Use both local and cloud backups.
• Update Software: Keep OS, browsers, and applications patched. Enable automatic updates.
• Use Antivirus: Install a real-time protection suite (e.g., Windows Defender, Bitdefender, Malwarebytes).
• Be Cautious: Avoid downloading cracked software or opening unsolicited email attachments.
• Disable Macros: Disable macros in Office documents by default.
• Network Segmentation: Separate critical systems from general user devices.

Remember: Paying the ransom does not guarantee file recovery and funds criminal activity. Always try decryption tools and backups first.