*[email protected]*.crypto

[Content by Gemini 2.5]

This resource provides a comprehensive overview of the ransomware variant identified by the file extension *[email protected]*.crypto. This variant is part of the prolific STOP/Djvu ransomware family, known for its widespread attacks targeting individual users and small to medium-sized businesses.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware encrypts files and appends a complex extension, typically in the format of .<original_extension>[email protected].
  • Renaming Convention: When a file is encrypted by this variant, its original name is preserved, but a new, multi-part extension is added.
    • Example: A file named document.docx would be renamed to [email protected].
    • This pattern ensures that the original file type is still visible (e.g., .docx), followed by the specific ransomware identifier which includes a contact email address ([email protected]) and a final .crypto suffix. This distinctive extension serves as a clear indicator of encryption by this specific ransomware strain.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants using the [email protected] email address, which are part of the broader STOP/Djvu ransomware family, have been actively observed since late 2022 to early 2024. The STOP/Djvu family itself has been rampant since late 2018, with new variants continually emerging. This particular extension pattern indicates a recent iteration within this ongoing threat landscape.

3. Primary Attack Vectors

*[email protected]*.crypto (like other STOP/Djvu variants) primarily relies on deceptive distribution methods to infect systems:

  • Cracked Software & Illegitimate Downloads: The most common vector involves embedding the ransomware into “cracked” versions of legitimate software (e.g., Photoshop, Microsoft Office, video games, system optimizers) available on torrent sites, file-sharing platforms, or dubious download portals. Users seeking free or pirated software often unknowingly execute the ransomware payload.
  • Fake Software Updates: Malicious websites or pop-ups prompting users to install “critical updates” for web browsers, Flash Player, or other common software can lead to the download and execution of the ransomware.
  • Malvertising & Drive-by Downloads: Redirects from compromised websites or malicious advertisements (malvertising) can sometimes initiate drive-by downloads, installing the ransomware without explicit user interaction (though modern browsers and OSes offer some protection against this).
  • Phishing Campaigns (Less Common for Initial Payload): While less prevalent for initial STOP/Djvu infections compared to other ransomware, targeted phishing emails with malicious attachments (e.g., infected Word documents with macros, ZIP archives containing executables) or links to compromised sites can also serve as an entry point.
  • Remote Desktop Protocol (RDP) Exploits: While not a primary vector for initial infection of individual users by STOP/Djvu, compromised RDP credentials or weakly secured RDP configurations can be exploited to gain access to a network, from which the ransomware can then be manually deployed. This is more common in attacks against businesses.
  • Software Vulnerabilities: While less frequently exploited by Djvu specifically, any unpatched software vulnerability (e.g., in operating systems, web browsers, or plugins) could theoretically be leveraged for silent infection.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are crucial to mitigate the risk of *[email protected]*.crypto 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/cloud). Ensure backups are stored offline or in cloud solutions with versioning to prevent ransomware from encrypting them.
  • Software Updates & Patching: Keep your operating system (Windows, macOS), web browsers, antivirus software, and all installed applications fully updated. Enable automatic updates where possible.
  • Reputable Antivirus/Anti-Malware: Install and maintain a reputable antivirus/anti-malware solution with real-time protection. Ensure its definitions are up-to-date.
  • Strong Password Practices: Use strong, unique passwords for all accounts. Employ multi-factor authentication (MFA) wherever available.
  • User Account Control (UAC): Do not disable UAC on Windows, as it helps prevent unauthorized changes to your system.
  • Email Vigilance: Be cautious of unsolicited emails, especially those with attachments or links. Verify the sender before clicking anything.
  • Avoid Illegitimate Software: Never download software from unofficial sources, torrent sites, or cracked software portals. These are primary distribution channels for STOP/Djvu.
  • Disable RDP if Not Needed: If you don’t require Remote Desktop Protocol, disable it. If it’s necessary, secure it with strong passwords and network-level authentication.

2. Removal

Once infected, swift and thorough removal is essential to prevent further damage:

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disconnect Wi-Fi). This prevents the ransomware from spreading to other devices on your network.
  2. Identify and Stop Ransomware Processes: Boot the system into Safe Mode with Networking (if necessary, though full scans often work in regular mode). Use Task Manager to identify and terminate any suspicious processes, although ransomware often auto-terminates after encryption.
  3. Perform a Full System Scan: Use your updated antivirus/anti-malware software (e.g., Malwarebytes, Kaspersky, Avast, Windows Defender) to perform a deep scan of the entire system. Allow the software to quarantine or remove all detected threats.
  4. Remove Persistent Elements: Check common ransomware persistence locations:
    • Startup Folders: shell:startup
    • Run Registry Keys: HKCU\Software\Microsoft\Windows\CurrentVersion\Run, HKLM\Software\Microsoft\Windows\CurrentVersion\Run
    • Scheduled Tasks: taskschd.msc
    • Be cautious when manually editing the registry; it’s generally safer to rely on reputable anti-malware tools.
  5. Restore HOSTS File: STOP/Djvu variants often modify the Windows HOSTS file (C:\Windows\System32\drivers\etc\hosts) to block access to security-related websites (antivirus vendors, cybersecurity forums). Restore it to its default state or remove malicious entries. You can usually find a default hosts file online or use a dedicated tool.
  6. Change All Passwords: After ensuring the system is clean, change all passwords used on the infected system (email, banking, social media, network shares) from a separate, clean device, as credentials might have been compromised.

3. File Decryption & Recovery

  • Recovery Feasibility: The feasibility of decrypting files encrypted by *[email protected]*.crypto largely depends on whether the ransomware used an offline key or an online key for encryption.
    • Offline Key: If the ransomware failed to establish a connection with its command-and-control server during encryption, it uses a pre-generated “offline” key. Files encrypted with offline keys may be decryptable if the master offline key for that specific variant has been recovered by security researchers.
    • Online Key: If the ransomware successfully connected to its server, it requests a unique “online” encryption key for the victim. Files encrypted with online keys are generally not decryptable without the specific private key held by the attackers.
  • Methods or Tools Available:
    • Emsisoft Decryptor for STOP/Djvu Ransomware: This is the primary tool for attempting decryption. Emsisoft, in collaboration with security researchers, regularly updates its decryptor with new keys as they are discovered.
      • How it works: You download the tool, select an encrypted file and its original (unencrypted) version (if available, which helps the decryptor identify the correct key), and the tool attempts to decrypt your files. It will indicate whether your files were encrypted with an offline or online key.
      • Availability: Downloadable from Emsisoft’s official website.
    • Data Recovery Software: For files that were not encrypted but perhaps deleted by the ransomware (e.g., Shadow Volume Copies), data recovery software (like PhotoRec, Recuva, or EaseUS Data Recovery) might be able to retrieve deleted content, but success is not guaranteed.
    • Shadow Volume Copies: STOP/Djvu variants typically attempt to delete Shadow Volume Copies (Windows backups) to hinder recovery efforts. However, in some cases, a few might remain or be recoverable via specialized tools.
  • Essential Tools/Patches:
    • Reputable Antivirus/Anti-Malware Software: Crucial for both prevention and removal.
    • Emsisoft Decryptor for STOP/Djvu: The go-to tool for potential decryption.
    • Windows Security Updates: Ensure your OS is fully patched to close known vulnerabilities.
    • Backup Software/Cloud Services: Indispensable for recovery if decryption is not possible.

4. Other Critical Information

  • Additional Precautions:
    • Ransom Note: *[email protected]*.crypto will leave a ransom note, typically named _readme.txt, in every folder containing encrypted files. This note contains instructions for payment, the [email protected] contact email address, and often a Telegram or Tox ID. Do not contact the attackers or pay the ransom, as there’s no guarantee of decryption, and it fuels future attacks.
    • HOSTS File Modification: As mentioned, verify and restore your HOSTS file as the ransomware commonly blocks access to cybersecurity websites to prevent victims from seeking help.
    • Information Stealer Module: Many STOP/Djvu variants bundle an information-stealing module (like RedLine Stealer or Vidar Stealer). This module attempts to steal passwords, cryptocurrency wallets, browser data, and other sensitive information from the infected system. Even if you recover your files, assume your personal data has been compromised and change all critical passwords from a clean device.
  • Broader Impact:
    • Massive Scale: The STOP/Djvu family is one of the most prolific ransomware threats globally, primarily targeting individual users and small businesses, causing significant financial and data loss.
    • Constant Evolution: New variants emerge frequently, often with minor changes to the file extension, contact email, or slight tweaks to the encryption routine, making consistent decryption a challenge.
    • Psychological Toll: Beyond data loss, victims often experience significant stress and anxiety, especially when personal photos or important documents are encrypted.
    • Economic Impact: While individual ransoms are relatively small (typically $490-$980), the cumulative economic impact from data loss, recovery efforts, and lost productivity is substantial.