@dr.com

[Content by Gemini 2.5]

This resource provides a detailed technical breakdown and practical recovery strategies for the ransomware variant identified by the file extension @dr.com. This variant is part of the widely known and prolific Djvu/STOP ransomware family, which constantly evolves and appends new, often unique, extensions to encrypted files.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this particular variant is @dr.com. This string is appended to the end of encrypted files.
  • Renaming Convention: The typical file renaming pattern employed by @dr.com (and other Djvu/STOP variants) is to append the [email protected] extension to the original filename and its original extension.
    • Example: A file named document.docx would become [email protected].
    • Example: A file named photo.jpg would become [email protected].
      This pattern allows the ransomware to easily identify which files it has already encrypted.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants of the Djvu/STOP ransomware family, of which @dr.com is one, began their widespread distribution around late 2018 and early 2019. This family has maintained a consistent and high level of activity since then, continuously releasing new variants with different file extensions. The @dr.com variant specifically would have emerged during this ongoing period of activity.

3. Primary Attack Vectors

  • Propagation Mechanisms: Djvu/STOP ransomware, including the @dr.com variant, primarily relies on social engineering and deceptive distribution channels rather than sophisticated network exploits. Its main methods of propagation include:
    • Cracked Software & Keygens: This is the most prevalent method. Users seeking pirated software, cracked versions of legitimate applications, key generators, or license activators often download installers that are secretly bundled with the ransomware.
    • Fake Software Updates: Malicious websites or pop-ups may trick users into downloading fake software updates (e.g., for Flash Player, Java, web browsers) that contain the ransomware payload.
    • Malicious Websites & Downloads: Visiting compromised websites or downloading files from unofficial sources (e.g., torrent sites, file-sharing platforms, dubious download portals) can lead to infection.
    • Malvertising: Malicious advertisements on legitimate websites can redirect users to infected sites or trigger drive-by downloads.
    • Email Phishing (Less Common for Djvu/STOP): While less common than for other ransomware families, some variants might be delivered via phishing emails containing malicious attachments (e.g., seemingly legitimate documents with macros) or links to malicious sites.
    • Remote Desktop Protocol (RDP) Exploits: While not a primary method for Djvu/STOP, poorly secured RDP connections can always serve as an entry point for manual deployment of ransomware by attackers.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    1. Regular Backups: Implement a robust backup strategy following the 3-2-1 rule (3 copies of data, 2 different media types, 1 offsite/cloud). Ensure backups are isolated from the network to prevent encryption.
    2. Antivirus/Anti-Malware Software: Install and maintain reputable endpoint detection and response (EDR) or antivirus solutions with real-time protection. Keep them updated.
    3. Operating System & Software Updates: Apply all security patches and updates for your operating system and all installed software promptly. This helps close known vulnerabilities.
    4. Software Source Verification: Only download software from official, trusted sources. Avoid pirated software, cracks, keygens, and unofficial download sites.
    5. User Education: Educate users about the risks of downloading files from untrusted sources, clicking suspicious links, and opening unsolicited email attachments.
    6. Strong Passwords & MFA: Use strong, unique passwords for all accounts, especially those with administrative privileges. Enable Multi-Factor Authentication (MFA) wherever possible.
    7. Network Segmentation: Segment networks to limit lateral movement of ransomware in case of an infection.
    8. Disable SMBv1: Ensure Server Message Block version 1 (SMBv1) is disabled, as it’s a common target for older ransomware, though less relevant for Djvu/STOP’s primary vectors.

2. Removal

  • Infection Cleanup:
    1. Isolate Infected Systems: Immediately disconnect the infected computer from the network (both wired and Wi-Fi) to prevent further spread.
    2. Identify and Terminate Malicious Processes: Use Task Manager or a process explorer tool (e.g., Process Explorer) to identify and terminate any suspicious processes. The ransomware executable often runs from temporary folders.
    3. Boot into Safe Mode: Restart the computer in Safe Mode (with Networking, if necessary, for updates or tool downloads). This loads only essential services, often preventing the ransomware from fully executing.
    4. Scan and Remove: Perform a full system scan using a reputable and updated antivirus/anti-malware program (e.g., Malwarebytes, Windows Defender, Bitdefender, Emsisoft Anti-Malware). Ensure the definitions are up-to-date.
    5. Check for Persistence Mechanisms:
      • Startup Entries: Check msconfig (Startup tab, for older Windows) or Task Manager (Startup tab, for newer Windows) and Registry Editor (HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run) for suspicious entries.
      • Scheduled Tasks: Check Task Scheduler for newly created, suspicious tasks designed to re-execute the ransomware.
      • HOSTS File: The Djvu/STOP variants often modify the C:\Windows\System32\drivers\etc\hosts file to block access to security-related websites. Check this file and remove any suspicious entries.
    6. Delete Ransomware Executable: Once identified, delete the ransomware executable file and any associated dropped files.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption of files encrypted by @dr.com (and other Djvu/STOP variants) is complex and often depends on whether an “online” or “offline” encryption key was used.

    • Online Key: If the ransomware successfully connected to its command and control (C2) server during encryption, it used a unique, “online” key specific to your infection. In this case, decryption without the attacker’s key is generally impossible.
    • Offline Key: If the ransomware failed to connect to its C2 server, it might use a pre-set “offline” key. For these specific cases, decryption might be possible using a specialized decryptor tool.

  • Methods or Tools Available:

    • Emsisoft Decryptor for STOP/Djvu Ransomware: This is the most reputable and frequently updated tool for Djvu/STOP variants. It collects encrypted files and your ransom note (_readme.txt) to determine if an offline key was used and if decryption is possible.
      • How it works: The decryptor tries to match your files with known offline keys. It’s crucial to have at least one original (unencrypted) file pair (encrypted and original version of the same file) if possible, as this significantly aids the decryptor.
    • Data Recovery Software: For files whose shadow copies or original versions were deleted by the ransomware, data recovery software (e.g., Recuva, PhotoRec) might be able to recover older, unencrypted versions, but success is not guaranteed, especially if the drive has been in heavy use.
    • System Restore Points & Volume Shadow Copies: Djvu/STOP often attempts to delete Volume Shadow Copies using commands like vssadmin delete shadows /all /quiet. Check if they exist, but do not rely on them.

  • Essential Tools/Patches:

    • Emsisoft Decryptor for STOP/Djvu Ransomware: The primary tool for potential file decryption.
    • Reputable Antivirus/Anti-Malware: For detection and removal (e.g., Malwarebytes, Windows Defender, Bitdefender).
    • Data Backup Solution: Crucial for recovery if decryption is not possible.
    • Operating System & Software Updates: Critical for preventing initial infection and re-infection.

4. Other Critical Information

  • Additional Precautions & Unique Characteristics:

    • Ransom Note: @dr.com will drop a ransom note, typically named _readme.txt, in every folder containing encrypted files. This note instructs the victim on how to pay the ransom (usually via cryptocurrency) and provides an email address for contact.
    • HOSTS File Modification: A hallmark of Djvu/STOP is its attempt to block access to security-related websites (e.g., antivirus vendors, security blogs) by modifying the hosts file (C:\Windows\System32\drivers\etc\hosts). This prevents victims from seeking help or downloading security tools.
    • Shadow Copy Deletion: The ransomware typically uses vssadmin commands to delete all Volume Shadow Copies, making recovery via Windows’ native tools extremely difficult.
    • Disable Security Software: It often tries to disable or interfere with installed antivirus and anti-malware programs to prevent its detection and removal.
    • Info-Stealer Component: Many recent Djvu/STOP variants are known to also install an information-stealing Trojan (e.g., Azorult, Vidar) alongside the ransomware. This means your personal data, credentials, and cryptocurrency wallet information might also be compromised, even if you don’t pay the ransom.

  • Broader Impact:

    • Widespread Consumer Impact: Due to its reliance on cracked software and dubious downloads, Djvu/STOP ransomware disproportionately affects individual users and small businesses seeking “free” software, leading to significant personal data loss and financial distress.
    • Constant Evolution: The continuous release of new variants with different file extensions makes it a persistent threat, requiring ongoing updates to decryption tools and security measures.
    • Difficulty of Decryption: The prevalence of “online” keys means that a significant percentage of victims cannot decrypt their files without paying the ransom, highlighting the importance of robust backup strategies.
    • Dual Threat (Ransomware + Info-Stealer): The inclusion of information stealers elevates the threat, as victims face not only data loss but also potential identity theft and financial fraud, even if they choose not to pay the ransom for file decryption.