*[email protected]*.aqva

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As a cybersecurity expert specializing in ransomware, I’ve compiled a detailed resource on the ransomware variant identified by the file extension *[email protected]*.aqva. This variant bears the hallmarks of the prolific STOP/Djvu ransomware family, known for its widespread distribution and challenging decryption.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this ransomware variant is .aqva. However, in many observed cases of STOP/Djvu, the ransomware appends a more complex extension that incorporates an identifier or the contact email. Therefore, files encrypted by this specific variant will typically be renamed following a pattern like:
    [email protected]
    For example, document.docx might become [email protected].
  • Renaming Convention: The ransomware appends the [email protected] string to the original filename, often preserving the original file extension. This comprehensive suffix helps the attacker identify their specific encryption and also serves as a direct contact method in the filename itself, in addition to the ransom note.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants incorporating .aqva and similar qq.com email contacts as part of their extension or ransom notes have been observed as part of the broader STOP/Djvu ransomware family’s continuous evolution. STOP/Djvu has been active since late 2018/early 2019, with new .aqva variants appearing more recently, typically throughout 2023 and continuing into 2024. This family is known for its high frequency of new variants.

3. Primary Attack Vectors

*[email protected]*.aqva, like other STOP/Djvu variants, primarily relies on social engineering and deceptive distribution methods rather than exploiting sophisticated network vulnerabilities.

  • Propagation Mechanisms:
    • Bundled Software/Cracked Software: This is the most prevalent method. Users download seemingly legitimate software cracks, key generators, pirated games, or fake software installers from untrusted websites (e.g., torrent sites, free software download sites). The ransomware is hidden within these executable files.
    • Malicious Advertisements (Malvertising): Compromised ad networks or rogue advertisers push malicious ads that, when clicked, redirect users to pages hosting exploit kits or directly download the ransomware.
    • Fake Software Updates: Pop-ups or deceptive websites prompting users to “update” their Flash Player, Java, or web browser, which instead download the ransomware.
    • Email Phishing Campaigns: While less common for STOP/Djvu than for other ransomware families, generic phishing emails with malicious attachments (e.g., infected Word documents with macros, fake invoices, shipping notifications) can still be a vector.
    • Compromised Websites: Visiting legitimate but compromised websites that auto-download the malware (drive-by downloads) or trick users into downloading it.
    • Remote Desktop Protocol (RDP) Exploits (Less Common): While not its primary method, poorly secured RDP endpoints can be targeted if attackers brute-force weak credentials or exploit known vulnerabilities, though this is more typical for enterprise-level ransomware. For Djvu, it’s rare.

Remediation & Recovery Strategies:

1. Prevention

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

  • Regular Data Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, 2 different media types, 1 offsite). Ensure backups are isolated from the network to prevent encryption.
  • Software Updates: Keep your operating system, applications (especially web browsers, email clients, and document editors), and antivirus software fully patched and up-to-date.
  • Antivirus/Endpoint Protection: Use reputable antivirus or Endpoint Detection and Response (EDR) solutions with real-time protection and behavioral analysis capabilities. Keep definitions updated.
  • Email Vigilance: Be extremely cautious with unsolicited emails. Never open suspicious attachments or click on dubious links, even if they appear to come from a known sender.
  • Strong Passwords & MFA: Use strong, unique passwords for all accounts and enable Multi-Factor Authentication (MFA) wherever possible.
  • Software Sourcing: Only download software, games, and media from official, reputable sources. Avoid pirated content, cracks, and key generators, as these are primary infection vectors.
  • Network Segmentation: For organizations, segment your network to limit lateral movement of ransomware in case of an infection.
  • User Education: Train users to recognize phishing attempts, identify suspicious files, and understand the risks associated with downloading untrusted software.

2. Removal

Infection cleanup must be done carefully to prevent further spread and ensure complete eradication.

  • Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi) to prevent the ransomware from spreading to other devices.
  • Identify and Stop Processes: Boot the system into Safe Mode with Networking. Use Task Manager to identify and terminate suspicious processes. Ransomware often runs from AppData\Local or ProgramData folders.
  • Run a Full System Scan: Use a reputable, up-to-date antivirus/anti-malware suite (e.g., Malwarebytes, Windows Defender Offline Scan, ESET) to perform a full system scan. Allow the software to quarantine or remove detected threats.
  • Check Startup Entries & Scheduled Tasks: The ransomware often creates persistence mechanisms. Check msconfig (Startup tab) or Task Scheduler for suspicious entries and disable/delete them.
  • Delete Temporary Files and Browser Cache: Clean up all temporary files, browser caches, and download folders where the initial dropper might have been stored.
  • Change Passwords: Once the system is clean, change all passwords used on or accessible from the infected machine, especially for online services.

3. File Decryption & Recovery

  • Recovery Feasibility: Decrypting files encrypted by *[email protected]*.aqva is challenging and often not possible without paying the ransom or a specific decryption key.
    • STOP/Djvu variants typically use a combination of online and offline encryption keys.
    • Online Key: If your internet connection was active during encryption, the ransomware generates a unique online key for your system, which is sent to the attacker’s server. Without this specific key, generated for your machine, decryption is practically impossible.
    • Offline Key: In some rare cases (e.g., if there’s no internet connection when encryption occurs), the ransomware might use a static, pre-defined “offline key.” If this offline key is known to security researchers, decryption might be possible.
  • Methods or Tools Available:
    • Emsisoft Decryptor for STOP/Djvu Ransomware: This is the primary tool for attempted decryption. It’s developed by Emsisoft in collaboration with ransomware researchers (like Michael Gillespie).
      • How it works: You provide encrypted files and, if possible, an unencrypted original copy of one of the files. The tool attempts to match your encryption ID with known offline keys. If a match is found, or if an online key for your specific ID has been leaked or recovered, it can decrypt your files.
      • Limitations: It can only decrypt files encrypted with a known offline key or if your specific online key is in their database. For new variants or unique online keys, it generally cannot help.
    • Shadow Volume Copies: Ransomware often attempts to delete Shadow Volume Copies (VSSAdmin Delete Shadows). However, sometimes it fails, or only partially succeeds. You can try using tools like ShadowExplorer to recover older versions of files. This is a long shot but worth trying.
    • Data Recovery Software: Tools like PhotoRec, Recuva, or Disk Drill can sometimes recover deleted original files before they were overwritten by the encrypted versions. This is highly dependent on disk usage after encryption and generally has a low success rate.
    • Professional Data Recovery Services: As a last resort, specialized data recovery companies might be able to help, but this is usually very expensive and not guaranteed.
  • Essential Tools/Patches:
    • Antivirus/Anti-Malware Suite: A comprehensive and up-to-date solution (e.g., Kaspersky, Bitdefender, ESET, Malwarebytes) is crucial for detection and removal.
    • Windows Security Updates: Ensure your Windows OS is fully patched to prevent exploitation of known vulnerabilities.
    • Backup Software: Reliable backup solutions (e.g., Veeam, Acronis, cloud backups) are paramount for data recovery without paying ransom.
    • Ad Blockers: Browser extensions like uBlock Origin can reduce exposure to malvertising.
    • Application Whitelisting: For organizations, whitelisting only approved applications can prevent unauthorized executables (like ransomware) from running.

4. Other Critical Information

  • Additional Precautions:
    • Ransom Note: This variant will drop a ransom note, typically named _readme.txt, in every folder containing encrypted files and on the desktop. This note contains instructions for contacting the attackers (likely [email protected]) and payment demands. Do not contact the attackers or pay the ransom unless absolutely necessary and all other recovery options have been exhausted. Paying emboldens criminals and doesn’t guarantee file recovery.
    • Information Stealing Module: Many recent STOP/Djvu variants, including those using the .aqva extension, bundle an information-stealing module (e.g., Vidar, RedLine Stealer, AZORult). This module attempts to steal credentials, cryptocurrency wallet information, browser data, and other sensitive information from the infected system before encryption. Assume your sensitive data has been compromised. Change passwords for all critical online accounts (email, banking, social media, etc.) immediately after cleaning the system.
    • Persistence: The ransomware often creates new scheduled tasks or modifies existing ones to ensure it runs on system startup, even after reboot. It may also modify the Windows HOSTS file to block access to security-related websites.
  • Broader Impact:
    • Financial Loss: Direct loss from ransom payment (if chosen), and indirect losses from operational downtime, recovery costs, and potential data loss.
    • Data Loss: Irrecoverable loss of files if decryption is not possible and backups are unavailable or compromised.
    • Operational Disruption: Significant interruption to personal or business activities, leading to lost productivity and potential reputational damage.
    • Privacy Compromise: The inclusion of info-stealing modules means a high risk of personal and financial data theft, leading to further security risks like identity theft or fraudulent transactions.
    • Psychological Impact: The stress and anxiety associated with data loss and system compromise can be substantial.

By understanding the technical aspects and diligently applying these remediation and recovery strategies, individuals and organizations can significantly enhance their resilience against *[email protected]*.aqva and similar ransomware threats.