*[email protected]*.*

[Content by Gemini 2.5]

This document provides a detailed technical breakdown and comprehensive recovery strategies for the ransomware variant identified by the file extension pattern *[email protected]*.*. Based on current intelligence and common ransomware behaviors, this pattern strongly indicates a variant of the Stop/Djvu ransomware family, where .nullhexxx is the appended file extension and [email protected] is often the contact email address listed in the ransom note.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    While the pattern *[email protected]*.* is a descriptor, the actual file extension appended to encrypted files by this specific Stop/Djvu variant is .nullhexxx. The [email protected] component typically appears as the contact email address within the ransom note, or in some instances, is integrated into the full ransom extension (though .nullhexxx is the most common for this specific variant).

  • Renaming Convention:
    Upon encryption, the ransomware renames files by appending the .nullhexxx extension.

    • Example: A file named document.docx will become document.docx.nullhexxx.
    • Ransom Note: A ransom note, typically named _readme.txt, is created in every folder containing encrypted files, providing instructions for victims on how to contact the attackers and pay the ransom. This note often contains the [email protected] email address for communication.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    The Stop/Djvu ransomware family has been active since late 2018 and has evolved into hundreds of variants. The .nullhexxx variant specifically began to appear and gain prominence in late 2023 and early 2024, indicating it is a relatively recent addition to this prolific ransomware family’s arsenal. New Djvu variants are continuously released.

3. Primary Attack Vectors

*[email protected]*.* (Djvu/Stop ransomware) primarily relies on stealthy and deceptive propagation methods, often targeting individual users and small businesses rather than large enterprises (though they are not immune).

  • Propagation Mechanisms:
    • Cracked Software/Pirated Content: This is the most common vector. Users download torrents, keygens, software cracks, or illegal copies of copyrighted software/media from unofficial websites. These downloads are often bundled with the ransomware executable.
    • Fake Software Updates: Malicious websites or pop-ups may impersonate legitimate software update notifications (e.g., for Adobe Flash Player, Java, web browsers) and trick users into downloading the ransomware.
    • Malicious Downloads: Drive-by downloads from compromised websites, or downloads disguised as legitimate files (e.g., documents, installers) from untrusted sources.
    • Malvertising: Compromised ad networks or malicious advertisements on legitimate websites redirect users to pages hosting exploit kits or directly downloading the ransomware.
    • Phishing Campaigns: While less common than for other ransomware families, email attachments disguised as invoices, shipping notifications, or other legitimate documents can contain the ransomware executable or a malicious script to download it.
    • Fake Tech Support Scams: In some cases, victims of fake tech support scams might be instructed to download “diagnostic tools” which are, in fact, the ransomware.
    • USB Drives: Less common, but infection can occur via infected USB drives if auto-run is enabled or if the user manually executes a malicious file.
    • Remote Desktop Protocol (RDP) Exploits: While not a primary method for Stop/Djvu, weakly secured RDP connections can sometimes be exploited for initial access, allowing the attackers to manually deploy the ransomware.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are crucial to minimize the risk of a *[email protected]*.* (Djvu/Stop) infection:

  • Regular Data Backups: Implement a robust backup strategy following the 3-2-1 rule (3 copies of data, 2 different media types, 1 offsite). Ensure backups are isolated from the network to prevent encryption.
  • Keep Software Updated: Regularly patch and update your operating system (Windows, macOS, Linux) and all installed software (browsers, plugins, antivirus, etc.) to close known security vulnerabilities.
  • Use Reputable Antivirus/Anti-Malware Software: Install and maintain a comprehensive security suite with real-time protection and behavioral analysis capabilities. Keep its definitions up-to-date.
  • Implement Email and Web Filtering: Use spam filters, email gateways, and web filters to block malicious attachments, links, and access to known malicious websites.
  • Educate Users: Train employees and family members about phishing, social engineering tactics, and the dangers of downloading cracked software or files from untrusted sources.
  • Disable Unnecessary Services: Turn off services like SMBv1, PowerShell remoting, or RDP if they are not essential, or secure them with strong passwords and network-level authentication.
  • Strong Passwords & Multi-Factor Authentication (MFA): Use complex, unique passwords for all accounts, and enable MFA wherever possible, especially for critical services.
  • Least Privilege Principle: Ensure users and applications operate with only the minimum necessary permissions.

2. Removal

If infected by *[email protected]*.*, follow these steps to remove the ransomware:

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi) to prevent further spread to other devices.
  2. Identify and Quarantine: Use a reputable antivirus or anti-malware tool (e.g., Malwarebytes, Emsisoft Anti-Malware, Windows Defender) to perform a full system scan. Allow the tool to quarantine or delete detected ransomware components. You might need to boot into Safe Mode with Networking if the ransomware is preventing normal operation.
  3. Check Startup and Scheduled Tasks: Manually review startup programs (Task Manager > Startup tab, msconfig) and scheduled tasks (Task Scheduler) for any suspicious entries that could re-launch the ransomware. Remove or disable them.
  4. Delete Shadow Copies: Djvu/Stop ransomware often attempts to delete Volume Shadow Copies to hinder recovery. Even if some are deleted, check for remaining ones, but rely primarily on your isolated backups.
    • Open Command Prompt as Administrator and run: vssadmin delete shadows /all /quiet (Use with caution as this deletes all shadow copies).
  5. Clean Temporary Files: Delete temporary files and browser caches that might contain remnants of the infection.

3. File Decryption & Recovery

  • Recovery Feasibility:
    For the .nullhexxx variant of Stop/Djvu ransomware, decryption without paying the ransom is generally NOT possible for the majority of victims.

    • Online vs. Offline Keys: Stop/Djvu variants typically use either “online” or “offline” encryption keys.
      • Online Key: If the ransomware connects to its Command & Control (C2) server during encryption, it generates a unique, online key for your system. This key is stored on the attackers’ server, making decryption without their cooperation impossible. Most new Djvu variants, including .nullhexxx, use online keys.
      • Offline Key: If the ransomware fails to connect to its C2 server, it uses a pre-defined, offline key. If security researchers manage to recover this specific offline key, then it might be possible to decrypt files using a publicly available decryptor. However, for a newly active variant like .nullhexxx, offline keys are rare, and finding a matching key is highly improbable.
    • Emsisoft Decryptor for STOP Djvu: Emsisoft, in cooperation with Emsisoft and the No More Ransom! project, provides a decryptor for many older Stop/Djvu variants. However, it is unlikely to work for newer variants like .nullhexxx that predominantly use online keys. You can try it, but manage your expectations. It requires an encrypted file and its original, unencrypted version to attempt finding a key, or an ID from the ransom note.
    • Paying the Ransom: Paying the ransom is strongly discouraged. There is no guarantee that attackers will provide a working decryptor, and it funds their criminal activities.

  • Essential Tools/Patches for Recovery:

    • Reliable Backups: This is your primary and most effective recovery method. If you have recent, uninfected backups stored offline, restore your data from them.
    • Emsisoft Decryptor for STOP Djvu: (As mentioned, try with caution and limited expectation for newer variants). Available from Emsisoft or No More Ransom! website.
    • Shadow Explorer: This tool can help you browse and retrieve previous versions of files from Windows Volume Shadow Copies. However, as noted, the ransomware often attempts to delete these.
    • Data Recovery Software: In some rare cases, if only file headers were encrypted or if the encryption process was interrupted, data recovery software might be able to retrieve some data, but this is highly speculative for ransomware infections.

4. Other Critical Information

  • Unique Characteristics (as a Djvu Variant):

    • Rapid Variant Release: The Djvu family is infamous for its continuous release of new variants (like .nullhexxx), each using a slightly different extension. This rapid evolution makes it hard for decryptors to keep up.
    • Offline vs. Online Key Dilemma: The distinction between online and offline keys is critical. Newer variants heavily favor online keys, significantly reducing the chance of free decryption.
    • Deletes Shadow Copies: A standard tactic is to attempt to delete shadow copies to hinder system restore and file recovery.
    • Modifies Hosts File: Some Djvu variants modify the Windows hosts file to block access to security-related websites, preventing victims from downloading antivirus tools or seeking help. Check and revert changes to C:\Windows\System32\drivers\etc\hosts.
    • Fake Decryptor Scams: Be extremely wary of websites or services claiming to offer guaranteed decryption for a fee (other than the original attackers). These are often scams that will take your money without providing a working decryptor.
    • No Free Decryptor for Newer Variants: Generally, if your files were encrypted with an online key by a recent Djvu variant, there is currently no free decryptor available.

  • Broader Impact:

    • Widespread Impact on Individuals: Djvu/Stop ransomware disproportionately affects individual users and small to medium-sized businesses due to its common distribution via consumer-focused channels (pirated software, malicious downloads).
    • Financial Loss: Victims face direct financial loss from the ransom demand and indirect costs from downtime, data loss, and recovery efforts.
    • Data Loss: For victims without robust backups, the data encrypted by *[email protected]*.* may be permanently lost.
    • Erosion of Trust: Leads to a general erosion of trust in online content and software downloads.
    • Continuously Evolving Threat: The constant stream of new Djvu variants underscores the persistent and evolving nature of ransomware threats, requiring continuous vigilance and adaptation in cybersecurity defenses.

By understanding these technical details and implementing the recommended prevention and recovery strategies, individuals and organizations can significantly bolster their defenses against *[email protected]*.* and similar ransomware threats.