*[email protected]*.kix

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This document provides a comprehensive analysis and practical guidance regarding the ransomware variant identified by the file extension *[email protected]*.kix. This variant is a part of the prolific STOP/Djvu ransomware family, known for its widespread impact on individual users and small businesses.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware encrypts files and appends the .kix extension to the original filename. The string [email protected] is the attacker’s contact email address, typically found within the ransom note, and serves as an identifier for this specific variant rather than being part of the file extension itself.

  • Renaming Convention: When a file is encrypted by this variant, its name will be altered according to the pattern:
    [original_filename].[kix_extension]
    For example:

    • document.docx becomes document.docx.kix
    • image.jpg becomes image.jpg.kix
    • archive.zip becomes archive.zip.kix

    In some cases, especially with more recent STOP/Djvu variants, a unique 4-character ID might be inserted before the final extension, e.g., document.docx.[random_ID].kix.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants using the .kix extension, linked to the [email protected] email, are relatively recent additions to the STOP/Djvu ransomware family. The STOP/Djvu family itself has been active since late 2018, with new variants being released almost daily. The .kix variant likely appeared in late 2023 or early 2024, following the continuous evolution and diversification of the Djvu threat.

3. Primary Attack Vectors

Like most STOP/Djvu variants, *[email protected]*.kix primarily relies on social engineering and deceptive distribution methods rather than exploiting network vulnerabilities for spread.

  • Propagation Mechanisms:
    • Bundled Software/Cracked Software: This is the most prevalent method. The ransomware is often distributed via torrent sites, illegal download portals, or compromised websites offering “free” cracked software, key generators (keygens), software activators, pirated games, or legitimate software bundled with malware. Users who download and execute these malicious installers unwittingly unleash the ransomware.
    • Malicious Email Attachments (Phishing): Though less common for Djvu than for some other ransomware families, spear-phishing or mass-phishing campaigns can be used. These emails contain deceptive attachments (e.g., fake invoices, shipping notifications, resumes) that, when opened, execute the ransomware payload.
    • Malvertising/Compromised Websites: Drive-by downloads or redirects from malicious advertisements or compromised legitimate websites can sometimes lead to infection if the user’s browser or plugins are unpatched.
    • Fake Software Updates: Pop-ups or alerts promoting urgent software updates (e.g., Flash Player, Java, web browsers) that, if clicked, download and execute the ransomware.
    • Remote Desktop Protocol (RDP) Exploits: While not a primary vector for Djvu, poorly secured RDP connections can be exploited by attackers to gain access to a system and manually deploy the ransomware.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are the most effective defense against *[email protected]*.kix and other ransomware.

  • Regular Data Backups: Implement a robust 3-2-1 backup strategy (3 copies, 2 different media types, 1 offsite). Ensure backups are isolated from the network to prevent encryption. Test restoration regularly.
  • Software Updates & Patching: Keep your operating system (Windows, macOS), web browsers, antivirus software, and all installed applications updated to their latest versions. Attackers often exploit known vulnerabilities that have available patches.
  • Antivirus/Anti-Malware Solutions: Install and maintain a reputable antivirus and anti-malware program with real-time protection. Ensure definitions are updated frequently.
  • Email Security: Be extremely cautious with unsolicited emails. Never open attachments or click links from unknown senders. Verify the legitimacy of emails, even from known contacts, if something seems suspicious.
  • User Education: Train users to recognize phishing attempts, identify suspicious links, and understand the risks associated with downloading software from untrusted sources.
  • Strong Passwords & MFA: Use strong, unique passwords for all accounts and enable Multi-Factor Authentication (MFA) wherever possible, especially for critical systems and remote access.
  • Network Segmentation: Isolate critical systems and sensitive data on separate network segments to limit lateral movement in case of an infection.
  • Disable Unnecessary Services: Turn off services like SMBv1, PowerShell remoting, or RDP if not strictly needed. If RDP is required, secure it with strong passwords, MFA, and restrict access to trusted IPs.

2. Removal

If your system is infected, follow these steps to remove *[email protected]*.kix and contain the infection. Do NOT pay the ransom.

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug the Ethernet cable, disable Wi-Fi). This prevents the ransomware from spreading to other devices on your network.
  2. Identify and Stop Ransomware Processes:
    • Boot into Safe Mode with Networking if possible, as some ransomware processes may not run in this mode.
    • Open Task Manager (Ctrl+Shift+Esc) and look for suspicious processes with unusual names or high CPU/memory usage. End them if you can identify them as malicious.
  3. Scan and Remove Malware:
    • Use a reputable antivirus/anti-malware program (e.g., Malwarebytes, ESET, Bitdefender, Windows Defender) to perform a full system scan. Ensure the antivirus definitions are up-to-date.
    • Allow the software to quarantine or remove all detected threats. Multiple scans may be necessary.
    • Consider using a bootable antivirus rescue disk for a deeper scan, as the ransomware might hinder software running from the compromised OS.
  4. Check for Persistence Mechanisms:
    • Examine startup folders, registry run keys, and scheduled tasks for any entries related to the ransomware. Remove any malicious entries.
    • The Djvu family often modifies the hosts file (C:\Windows\System32\drivers\etc\hosts) to block access to security-related websites (e.g., antivirus vendors). Check this file and remove any suspicious entries.
  5. Clean Up Temporary Files: Delete temporary files and browser caches, as they might contain remnants of the infection.

3. File Decryption & Recovery

  • Recovery Feasibility: The possibility of decrypting files encrypted by *[email protected]*.kix largely depends on the encryption key used:

    • Offline Key: If the ransomware failed to establish communication with its command-and-control server during encryption, it might use a pre-generated “offline key.” In this scenario, decryption is often possible if the specific offline key used by your variant is known and integrated into public decryptors.
    • Online Key: If the ransomware successfully communicated with its server, it will generate a unique “online key” for your system. Decryption with an online key is extremely difficult, if not impossible, without the attacker’s cooperation or a major cryptographic flaw in their implementation.

  • Methods or Tools Available:

    • Emsisoft Decryptor for STOP Djvu: This is the primary and most reliable tool for attempting decryption. Emsisoft, in collaboration with law enforcement and cybersecurity researchers, continuously updates its decryptor with new keys as they become available.
      • How to use: Download the Emsisoft Decryptor for STOP Djvu from their official website. Run it and follow the instructions. It will attempt to identify the key used and decrypt your files. Be aware that it may only decrypt files encrypted with offline keys.
    • System Restore Points: Ransomware often deletes Volume Shadow Copies. However, it’s worth checking if any restore points exist from before the infection. Go to System Properties > System Protection > System Restore.
    • Previous Versions: Right-click on encrypted files/folders and check “Restore previous versions.” This relies on Volume Shadow Copies, which are usually deleted by Djvu variants.
    • Data Recovery Software: Tools like PhotoRec, R-Studio, or EaseUS Data Recovery may be able to recover older, unencrypted versions of files that were deleted or overwritten during the encryption process, but success is not guaranteed.
    • Backups: The most reliable method of recovery is to restore your files from clean, offline backups created before the infection.

  • Essential Tools/Patches:

    • Emsisoft Decryptor for STOP Djvu: Crucial for decryption attempts.
    • Reputable Antivirus/Anti-Malware Software: For detection and removal (e.g., Malwarebytes, Bitdefender, Kaspersky, ESET, Windows Defender).
    • Operating System Updates: Keep Windows (or macOS) fully patched.
    • Browser and Application Updates: Ensure all commonly used software is updated.

4. Other Critical Information

  • Additional Precautions/Unique Characteristics:

    • Ransom Note: This variant typically drops a ransom note named _readme.txt in every folder containing encrypted files and on the desktop. This note contains instructions for payment and contact details for the attackers, specifically [email protected].
    • Hosts File Modification: As noted, Djvu variants commonly modify the hosts file to block access to cybersecurity websites, preventing victims from seeking help or downloading security tools.
    • Shadow Copy Deletion: The ransomware attempts to delete Volume Shadow Copies to hinder recovery attempts using System Restore or “Previous Versions.”
    • Information Stealer Bundling: Many STOP/Djvu variants are bundled with other malware, most notably information stealers like Vidar, RedLine, or SmokeLoader. Even if files are recovered, personal information (passwords, crypto wallets, browser data) might have been exfiltrated. A thorough post-infection cleanup and password reset for all online accounts are critical.

  • Broader Impact:

    • Financial Loss: Victims face the decision of paying the ransom (which is never guaranteed to result in decryption and funds the attackers) or incurring costs for professional data recovery/system cleanup.
    • Data Loss: If decryption is not possible and backups are unavailable, irreversible data loss occurs.
    • Operational Disruption: For businesses, infection leads to downtime, lost productivity, and potential reputational damage.
    • Identity Theft Risk: If an information stealer was also present, personal and financial data may be compromised, leading to further fraud or identity theft.
    • Emotional Distress: The experience of losing precious files can be highly stressful for individuals.

Always remember: Paying the ransom encourages future attacks. Focus on prevention and robust recovery strategies. If you are a victim, consider reporting the incident to your local law enforcement or cybersecurity authorities (e.g., FBI IC3 in the US, National Cyber Security Centre in the UK, local police cybercrime unit).