Remove STOP/DJVU Ransomware and Recover Encrypted Files

Symptoms

STOP/DJVU ransomware infection typically exhibits the following symptoms:

• Files (documents, images, databases) have extensions like .djvu, .tro, .udjvu, .djvuu, or similar.
• A _readme.txt ransom note appears in each folder containing encrypted files.
• Desktop wallpaper may be changed to a ransom message.
• System slowdown, unusual network activity, or pop-up ads (if bundled with other malware).
• Inability to open previously accessible files.

Root Causes

STOP/DJVU ransomware spreads through:

• Phishing emails with malicious attachments (e.g., fake invoices, shipping notices).
• Downloading cracked software, keygens, or pirated content from untrusted sites.
• Malicious advertisements (malvertising) or compromised websites.
• USB drives or external media infected with the ransomware.
• Exploiting outdated software vulnerabilities (e.g., old browser plugins).

Step-by-Step Fix

Step 1: Disconnect from the Internet

Immediately disconnect the infected computer from the internet and any network shares to prevent further encryption or spread.

Step 2: Boot into Safe Mode with Networking

1. Restart your PC and press F8 (or Shift + Restart in Windows 10/11) to access Advanced Boot Options.
2. Select Safe Mode with Networking.

Step 3: Download and Run Malwarebytes

1. On a clean computer, download Malwarebytes Anti-Malware (free version) and save it to a USB drive.
2. On the infected PC in Safe Mode, run the installer and update definitions.
3. Perform a Full Scan and remove all detected threats.

Step 4: Use STOP Decryptor (Emsisoft)

1. Visit Emsisoft STOP DJVU Decryptor on a clean computer and download the tool.
2. Transfer the tool to the infected PC via USB.
3. Run the decryptor as Administrator. It will attempt to decrypt files using offline keys.
4. If successful, your files will be restored. If not, the decryption may require an online key (which is harder to recover).

Step 5: Restore from Backup

If you have a clean backup (external drive, cloud), restore your files after removing the malware. Do not connect backups until the system is clean.

Alternative Fixes

• System Restore: Use Windows System Restore to revert to a point before infection. This may remove the ransomware but not always recover encrypted files.
• Shadow Volume Copies: Check if Volume Shadow Copy is enabled. Use tools like ShadowExplorer to recover previous versions of files.
• Professional Data Recovery: If files are critical and decryption fails, consider contacting a data recovery service (costly and not guaranteed).
• Reinstall Windows: As a last resort, perform a clean installation of Windows to ensure removal, but this will not recover files.

Prevention

• Regular Backups: Maintain 3-2-1 backup rule (3 copies, 2 different media, 1 offsite). Use both cloud and external drives.
• Keep Software Updated: Enable automatic updates for Windows, antivirus, and all applications.
• Use Antivirus: Install reputable security software (e.g., Malwarebytes, Bitdefender) and enable real-time protection.
• Be Cautious with Emails: Do not open attachments or click links from unknown senders. Verify unexpected invoices or shipping notices.
• Avoid Piracy: Do not download cracked software or keygens from untrusted sources.
• Disable Macros: In Microsoft Office, disable macros from untrusted documents.
• User Account Control (UAC): Keep UAC enabled to prevent unauthorized changes.

Important Notes

STOP/DJVU ransomware has many variants. The Emsisoft decryptor works for most offline-key variants. If your files have an online key (unique to your machine), decryption is extremely difficult. Never pay the ransom—there is no guarantee you will get your files back, and it funds criminal activity. Always consult with cybersecurity professionals if unsure.