*[email protected]*.*

[Content by Gemini 2.5]

The ransomware variant identified by the file extension containing *[email protected]*.* is a recent iteration belonging to the prolific STOP/Djvu ransomware family. This family is notorious for its frequent updates, making it a persistent threat to individuals and small to medium-sized businesses worldwide.

Below is a detailed breakdown of this variant and practical recovery strategies.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this variant is typically in the format of [email protected]. When a file is encrypted, the ransomware appends this string to the original filename.

  • Renaming Convention: The typical renaming pattern for encrypted files follows this structure:
    [original_filename].[original_extension].[4-character_ID][email protected]
    However, often the 4-character ID is omitted, and the pattern becomes:
    [original_filename].[original_extension][email protected]

    Example: A file named document.docx would be renamed to [email protected] or [email protected].

    The ransomware also drops a ransom note, typically named _readme.txt, in every folder containing encrypted files and on the desktop.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants incorporating email addresses like [email protected] are constantly emerging within the STOP/Djvu family. This specific variant was likely first detected in late 2023 or early 2024, continuing the ongoing wave of new STOP/Djvu versions. The STOP/Djvu family itself has been active since 2018 and consistently releases new variants.

3. Primary Attack Vectors

STOP/Djvu ransomware, including the [email protected] variant, primarily propagates through:

  • Bundled Software/Crackers/Keygens: This is the most prevalent method. Users download pirated software, game cracks, key generators, or software activators from untrusted sources (e.g., torrent sites, free software download sites). The ransomware is hidden within these seemingly legitimate files.
  • Malvertising & Drive-by Downloads: Malicious advertisements online can redirect users to compromised websites that silently download and execute the ransomware (drive-by downloads) or trick users into downloading malicious files.
  • Phishing Campaigns: While less common than software bundling for STOP/Djvu, targeted phishing emails with malicious attachments (e.g., seemingly legitimate documents with embedded macros) or links to infected sites can also be used.
  • Fake Updates: Prompts for fake software updates (e.g., Flash Player, Java) can lead to the download of the ransomware.
  • Remote Desktop Protocol (RDP) Exploitation (Less Common): While not a primary vector for this specific family, poorly secured RDP connections can be exploited by threat actors to manually deploy ransomware. However, this is more typical of enterprise-level ransomware campaigns. For STOP/Djvu, direct user interaction via bundled software is dominant.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are the most effective defense against ransomware like [email protected].

  • Robust Backup Strategy: Implement a 3-2-1 backup rule: at least three copies of your data, on two different media, with one copy off-site or offline (air-gapped). Regularly test your backups for integrity and restorability.
  • Software Updates & Patching: Keep your operating system, web browsers, antivirus software, and all applications (especially critical ones like Microsoft Office, Java, Adobe products) fully updated with the latest security patches. Enable automatic updates where possible.
  • Antivirus/Endpoint Detection & Response (EDR): Use a reputable, up-to-date antivirus or EDR solution. Ensure real-time protection is enabled.
  • User Education: Educate users about the dangers of downloading pirated software, clicking on suspicious links, opening unexpected email attachments, and the importance of verifying sender identities.
  • Email Security: Implement email filters to block malicious attachments and identify phishing attempts.
  • Firewall Rules: Configure your firewall to block unauthorized inbound and outbound connections.
  • Disable/Harden RDP: If RDP is necessary, secure it by using strong, unique passwords, multi-factor authentication (MFA), limiting access to specific IP addresses, and placing it behind a VPN.
  • Ad Blockers: Use browser ad-blockers to reduce exposure to malvertising.
  • Software Restriction Policies/Application Whitelisting: Implement policies to prevent the execution of unauthorized or suspicious executables.

2. Removal

Removing the ransomware from an infected system is crucial before attempting any recovery.

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi) to prevent further spread.
  2. Identify the Threat: Do NOT attempt to run programs from the infected machine if possible. Use a clean, uninfected computer to download reputable antimalware tools.
  3. Boot into Safe Mode with Networking: This limits the running processes, making it easier for security software to detect and remove the ransomware.
    • Windows 10/11: Settings > Update & Security (or System > Recovery) > Recovery > Advanced startup > Restart now. Then Troubleshoot > Advanced options > Startup Settings > Restart. Press 5 or F5 for “Enable Safe Mode with Networking”.
  4. Run a Full System Scan: Use a powerful and updated antimalware tool (e.g., Malwarebytes, Windows Defender Offline, ESET, Sophos) to perform a deep scan and remove all detected threats. Multiple scans with different tools might be necessary.
  5. Check Startup Items and Scheduled Tasks: Manually review and disable any suspicious entries in Task Manager (Startup tab) and Task Scheduler (Task Scheduler Library). Ransomware often sets itself to run at startup.
  6. Review Hosts File: Check C:\Windows\System32\drivers\etc\hosts for any suspicious entries that might redirect legitimate security sites or update servers.
  7. Delete Ransom Note and Stub Files: Once the ransomware executable is removed, delete the _readme.txt ransom notes and any residual files left by the ransomware (e.g., hidden executables in %AppData% or %Temp%).
  8. Change All Passwords: After confirming the system is clean, change all passwords used on the compromised machine (email, online banking, social media, etc.), especially for network or cloud services.

3. File Decryption & Recovery

  • Recovery Feasibility:

    • Offline IDs: For many STOP/Djvu variants, including [email protected], decryption is possible if the ransomware encrypted files using an “offline key.” This happens when the ransomware cannot establish a connection to its command-and-control (C2) server during encryption, forcing it to use a default, hardcoded key. Files encrypted with an offline key will often have a t1 suffix (e.g., t1) in the PersonalID.txt file (found in C:\SystemID\PersonalID.txt) or in the ransom note, but this isn’t always reliable.
    • Online IDs: If the ransomware successfully connected to its C2 server, it generated a unique, online key for your system. Decryption for online IDs is currently impossible without the specific private key from the attackers. Paying the ransom is strongly discouraged as there is no guarantee of decryption, and it fuels future ransomware attacks.

  • Essential Tools/Patches:

    • Emsisoft Decryptor for STOP/Djvu: This is the primary and most reliable tool for attempting decryption of STOP/Djvu variants. Download it from the official Emsisoft website.
      • How it works: You’ll need an original (unencrypted) file pair (the encrypted version and its original counterpart) or at least one encrypted file to help the decryptor identify the key. It attempts to match your encrypted files with known keys.
      • Important Note: The decryptor requires time and processing power. It may not work for all “online” encrypted files.
    • Data Recovery Software: Even if decryption isn’t possible, sometimes fragments of unencrypted files (e.g., previous versions, temporary files) might be recoverable using data recovery tools like PhotoRec or EaseUS Data Recovery Wizard, especially if Shadow Volume Copies were not deleted.
    • Windows System Restore / Shadow Volume Copies: STOP/Djvu variants often attempt to delete Shadow Volume Copies to hinder recovery. However, it’s worth checking if they exist:
      • Open “System Protection” (search for it in Windows).
      • Check if “Protection” is “On” for your drives.
      • If so, you might be able to use “System Restore” or restore previous versions of files/folders.
      • Command to check/delete shadow copies (run as admin in PowerShell): vssadmin list shadows (to list) or vssadmin delete shadows /all /quiet (what ransomware often runs).
    • Microsoft Windows Updates: Ensure your system is fully patched to prevent exploitation of common vulnerabilities.

4. Other Critical Information

  • Additional Precautions:

    • Information Gathering: Before taking any recovery steps, back up the ransom note (_readme.txt) and the PersonalID.txt (if present) as they contain crucial information (like your ID and contact email) that might be needed for decryption tools or analysis.
    • Don’t Trust Free Decryptors from Unknown Sources: Only use decryptors from reputable cybersecurity firms (like Emsisoft, No More Ransom). Scammers often distribute fake decryptors that can cause more damage.
    • Shadow Copy Deletion: This variant, like other STOP/Djvu versions, typically uses the vssadmin.exe delete shadows /all /quiet command to remove all shadow volume copies, significantly complicating recovery via Windows built-in features.
    • Hosts File Modification: Some variants may modify the hosts file to block access to security websites. Always check this file after an infection.

  • Broader Impact:

    • Financial Burden: The primary impact is the financial cost of potential data loss, recovery efforts, or, in rare and discouraged cases, the ransom payment.
    • Operational Disruption: For businesses, encryption leads to significant downtime, loss of productivity, and potential reputational damage.
    • Data Loss: If decryption is not possible and backups are inadequate, permanent data loss is a severe consequence.
    • Emotional Stress: For individuals, the loss of personal photos, documents, and other irreplaceable files can be highly distressing.
    • Prevalence: The STOP/Djvu family, due to its low-sophistication attack vectors and constant variant releases, remains one of the most widespread consumer-level ransomware threats.