*[email protected]*.bin

[Content by Gemini 2.5]

This resource provides a detailed technical breakdown and comprehensive recovery strategies for the ransomware variant identified by the file extension *[email protected]*.bin. Based on the file extension pattern, this variant strongly aligns with characteristics of the STOP/Djvu ransomware family, which frequently appends an email address (or part of it) within the custom extension.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by this ransomware variant will typically have an additional extension appended to their original name, which includes the specified email address. The exact final extension will be *[email protected].
  • Renaming Convention: The ransomware follows a pattern common to Djvu/STOP variants. An encrypted file originally named document.docx might become [email protected], where xxxx is a unique victim ID (usually 4 alphanumeric characters) or sometimes omitted, depending on the specific variant build. A ransom note, typically named _readme.txt, will be placed in every folder containing encrypted files.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: While *[email protected]*.bin refers to a specific build or variant, the underlying STOP/Djvu ransomware family has been continuously active and evolving since late 2018/early 2019. New variants with different appended extensions (like .bin, .qqqq, .zzza, etc., often including an email address) are released frequently, sometimes daily. This particular [email protected] variant would be a recent iteration within this ongoing campaign.

3. Primary Attack Vectors

The STOP/Djvu ransomware family primarily relies on social engineering and stealthy distribution methods:

  • Cracked Software/Pirated Content: The most prevalent method involves victims downloading cracked software, pirated games, key generators, software activators (e.g., KMSpico), or copyrighted media from untrustworthy websites. The ransomware payload is often bundled within these downloads.
  • Fake Software Updates: Malicious websites or pop-ups prompting users to install “critical updates” for legitimate software (like Flash Player, web browsers, or media players) can deliver the ransomware.
  • Malvertising/Malicious Ads: Redirects from legitimate websites to malicious ones, often through compromised ad networks, can lead to drive-by downloads or social engineering prompts to install malicious files.
  • Phishing Campaigns (Less Common for Djvu/STOP): While not its primary vector, carefully crafted phishing emails containing malicious attachments (e.g., weaponized documents with macros) or links to infected sites can also be used, though this is more typical for larger, enterprise-focused ransomware groups.
  • Software Vulnerabilities: Less common for Djvu/STOP, but unpatched vulnerabilities in common applications or operating systems could theoretically be exploited if the threat actors broaden their tactics. However, it does not typically exploit network vulnerabilities like EternalBlue or SMBv1 for widespread lateral movement like some other major ransomware families.

Remediation & Recovery Strategies:

1. Prevention

  • Regular Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, on 2 different media, with 1 copy off-site/offline). Ensure backups are immutable or regularly disconnected from the network to prevent encryption.
  • Antivirus/Endpoint Detection & Response (EDR): Install and maintain reputable antivirus or EDR solutions with real-time protection enabled. Ensure definitions are constantly updated.
  • Software and OS Updates: Keep your operating system, web browsers, and all installed software fully patched and updated. This closes security vulnerabilities that ransomware could exploit.
  • Firewall Configuration: Configure your firewall to block unauthorized inbound and outbound connections.
  • User Account Control (UAC): Do not disable UAC. It helps prevent unauthorized changes to your system.
  • Email and Browsing Hygiene: Be extremely cautious with unsolicited emails, suspicious attachments, and links. Avoid downloading software or media from unverified or pirated sources. Use an ad-blocker.
  • Disable Macros: Configure Microsoft Office to disable macros by default and only enable them for trusted documents.
  • Application Whitelisting: Consider implementing application whitelisting to prevent unauthorized executables from running.

2. Removal

  • Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi) to prevent further spread.
  • Identify Ransomware Processes: Use Task Manager (Windows) or process monitoring tools to identify suspicious processes. Djvu/STOP often creates processes like bguu.exe, wim.exe, build.exe, or randomly named executables in %AppData% or %LocalAppData%.
  • Boot into Safe Mode: Restart the computer in Safe Mode with Networking. This often prevents the ransomware from fully executing or establishing persistence.
  • Run a Full System Scan: Use a reputable antivirus/anti-malware program (e.g., Malwarebytes, Windows Defender in Safe Mode) with updated definitions to perform a full scan and remove all detected threats. Multiple scans with different tools may be beneficial.
  • Remove Persistence: Check common startup locations (MSConfig, Task Scheduler, Registry keys like HKCU\Software\Microsoft\Windows\CurrentVersion\Run) for entries related to the ransomware and remove them.
  • Delete Shadow Volume Copies: Ransomware often deletes Shadow Volume Copies to prevent easy restoration. However, it’s good practice to try to recover them if not deleted, or ensure future backups include them. Use vssadmin delete shadows /all /quiet (use with caution, as this removes all restore points).

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption feasibility for STOP/Djvu ransomware depends heavily on whether the victim’s machine was connected to the attacker’s command-and-control (C2) server during encryption, leading to an “online ID” or “offline ID.”
    • Online ID: If connected, a unique encryption key is generated and stored on the C2 server. Decryption is generally NOT possible without paying the ransom and obtaining the key from the attackers.
    • Offline ID: If the C2 server was unreachable (e.g., due to network issues on the victim’s end or server downtime), the ransomware encrypts files using a pre-generated, static “offline” key. For these cases, decryption IS often possible.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP/Djvu: This is the primary tool for decrypting files encrypted by STOP/Djvu variants. It requires collecting encrypted files and their original unencrypted counterparts (if available) to identify the encryption key (especially for offline IDs). The decryptor continuously updates its database with new keys. You can download it from the Emsisoft website.
    • STOPDecrypter (by Michael Gillespie/Emsisoft): This tool attempts to identify the specific Djvu variant based on the encrypted files and offers a path to decryption if a key is known.
    • Data Recovery Software: In some cases, if shadow copies were not deleted or files were only partially encrypted, data recovery software might retrieve older, unencrypted versions of files. However, success rates vary greatly.
    • System Restore Points: If system restore points exist from before the infection, you might be able to roll back your system, though this won’t recover encrypted data unless it existed outside the infected partition or was backed up.
    • Backups: The most reliable method for file recovery is restoring from clean, recent backups.

4. Other Critical Information

  • Unique Characteristics:
    • _readme.txt Ransom Note: This specific file name is a hallmark of the STOP/Djvu family.
    • Info.txt File: Often, an info.txt file (or similar, like PersonalID.txt) is dropped in the C:\SystemID folder containing the victim’s unique ID and the attacker’s public key hash. This file is crucial for decryption attempts.
    • Heavy Obfuscation: The ransomware executable is typically heavily obfuscated to evade detection by antivirus software.
    • Self-Deletion: After encryption, the ransomware often attempts to delete its own executable to hide its tracks.
  • Broader Impact:
    • Widespread Consumer Impact: STOP/Djvu primarily targets individual users and small businesses, making it one of the most widespread consumer-facing ransomware families due to its distribution methods.
    • Low Payouts, High Volume: While individual ransom demands are relatively low (often $490-$980), the high volume of infections makes it profitable for the attackers.
    • Evolving Nature: The rapid release of new variants (with different file extensions) makes it a persistent threat, requiring constant updates from security researchers and antivirus vendors.
    • Risk of Secondary Infections: The cracked software/pirated content vector often means victims may also be infected with other malware (e.g., info-stealers, cryptocurrency miners) alongside the ransomware. It is critical to perform thorough system scans after ransomware removal.
    • No Guarantee of Decryption: Even if the ransom is paid, there is no guarantee that the attackers will provide a working key or that the decryption process will be successful. Security experts universally advise against paying the ransom.