*[email protected]*[email protected]

[Content by Gemini 2.5]

This document provides a detailed resource on the ransomware variant identified by the file extension *[email protected]*[email protected]. This variant is part of the STOP/Djvu ransomware family, a prolific and constantly evolving threat primarily targeting individual users and small businesses.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this variant is [email protected]@bigmir.net. This specific pattern helps in identifying the ransomware.

  • Renaming Convention: When a file is encrypted by this ransomware, its original name is altered to include the unique extension. The typical renaming pattern is:
    [original_filename].[original_extension][email protected]@bigmir.net

    Examples:

    The ransomware encrypts the file and appends its unique identifier string to the end of the filename.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The STOP/Djvu ransomware family, to which this variant belongs, first emerged in late 2018 / early 2019. Since then, it has maintained a consistent and high-volume presence, releasing new variants almost daily. The specific [email protected]@bigmir.net variant would have appeared sometime within this ongoing timeline as part of the family’s continuous evolution. It is a recurring and persistent threat.

3. Primary Attack Vectors

STOP/Djvu ransomware, including the [email protected]@bigmir.net variant, primarily relies on social engineering and deceptive practices to infect systems. Unlike some enterprise-focused ransomware that leverages advanced network exploits, Djvu often targets individual users through:

  • Bundled Software/Freeware/Shareware: This is the most common method. The ransomware is often hidden within installers for pirated software (e.g., cracked versions of games, productivity software like Adobe Photoshop, Microsoft Office), key generators (keygens), software loaders, and other seemingly legitimate freeware downloaded from unofficial or shady websites.
  • Malicious Websites and Downloads: Users downloading software from untrustworthy sources, torrent sites, or file-sharing platforms are at high risk. The ransomware executable might be disguised as a setup file, a patch, or a crack.
  • Fake Software Updates: Pop-ups or deceptive websites prompting users to install “critical updates” for web browsers, media players, or other common software can lead to the download and execution of the ransomware.
  • Malvertising: Less common for initial infection, but malicious advertisements on compromised websites can sometimes redirect users to download sites hosting the ransomware.
  • Phishing Campaigns: While less sophisticated than targeted spear-phishing, some Djvu variants might be distributed via email attachments (e.g., fake invoices, shipping notifications) that contain malicious macros or direct executable downloads, often targeting less tech-savvy users.
  • Remote Desktop Protocol (RDP) Exploits: While not a primary method for Djvu (more common for enterprise ransomware like Ryuk or Conti), weakly secured RDP access can occasionally be exploited to gain initial access, after which the ransomware could be manually deployed.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are crucial to prevent infection by *[email protected]*[email protected] and other ransomware variants:

  • Regular Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, 2 different media types, 1 offsite). Ensure backups are immutable or offline to prevent them from being encrypted.
  • Strong Antivirus/Endpoint Detection and Response (EDR): Use reputable and up-to-date antivirus or EDR solutions with real-time protection.
  • Software and OS Updates: Keep your operating system (Windows, macOS, Linux) and all installed software patched and updated to close known security vulnerabilities.
  • User Education: Educate users about the dangers of downloading software from unofficial sources, clicking suspicious links, and opening unknown email attachments. Emphasize the risks associated with pirated software.
  • Disable Unnecessary Services: Turn off services like SMBv1, PowerShell, and RDP if not strictly needed. If RDP is required, secure it with strong passwords, multi-factor authentication (MFA), and network-level authentication (NLA), and restrict access to trusted IPs.
  • Firewall Configuration: Implement a firewall to block suspicious connections and restrict outbound traffic from sensitive systems.
  • Application Whitelisting: Consider implementing application whitelisting policies to prevent unauthorized executables from running.

2. Removal

If a system is infected, follow these steps to remove the *[email protected]*[email protected] ransomware:

  1. 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.
  2. Identify and Terminate Malicious Processes:
    • Open Task Manager (Ctrl+Shift+Esc or Ctrl+Alt+Del -> Task Manager).
    • Look for suspicious processes with unusual names or high CPU/memory usage.
    • Right-click and “End Task.” Be cautious, as some ransomware processes may masquerade as legitimate system processes.
  3. Boot into Safe Mode: Restart your computer and boot into Safe Mode with Networking. This loads only essential services and drivers, often preventing the ransomware from fully executing.
  4. Perform a Full System Scan:
    • Use a reputable anti-malware software (e.g., Malwarebytes, ESET, SpyHunter, Avast, AVG, Windows Defender) to perform a deep scan of the entire system.
    • Allow the software to quarantine or remove all detected threats.
    • Multiple scans with different tools may be beneficial.
  5. Remove Ransom Notes: Locate and delete all ransom notes (e.g., _readme.txt) from your desktop and affected folders.
  6. Check for Persistence Mechanisms:
    • Startup Folders: Check shell:startup and shell:common startup in the Run dialog (Win+R).
    • Registry Editor (regedit.exe): Look for suspicious entries in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run.
    • Task Scheduler: Check taskschd.msc for newly created scheduled tasks designed to re-execute the ransomware.
  7. Restore Host File: Ransomware often modifies the Windows Hosts file (C:\Windows\System32\drivers\etc\hosts) to block access to security-related websites. Check and restore it to its default state if modified.

3. File Decryption & Recovery

  • Recovery Feasibility: The feasibility of decrypting files encrypted by *[email protected]*[email protected] (and other STOP/Djvu variants) depends on whether an online key or an offline key was used during encryption:
    • Online Key: If the ransomware successfully connected to its command-and-control (C2) server, it fetches a unique encryption key for the victim. Decryption using an online key is generally not possible without the attackers’ key, as each key is unique. New Djvu variants almost exclusively use online keys.
    • Offline Key: In some rare cases (e.g., if the C2 server is unreachable during encryption), the ransomware uses a pre-generated “offline” key. If security researchers manage to recover this offline key (e.g., from a sample of the malware), a decryptor tool can be developed.
    • Emsisoft Decryptor for STOP/Djvu: Emsisoft, in collaboration with security researchers, has developed a free decryptor for many STOP/Djvu variants. You can download it from their official website.
      • Important: The Emsisoft decryptor only works for variants where an offline key has been identified and added to their database, or for specific online keys that have been compromised. For most recent online-key-encrypted files, it will unfortunately not work.
      • You can submit an encrypted file and the ransom note to Emsisoft’s online checker or ID Ransomware (www.id-ransomware.malwarehunterteam.com) to determine if a decryptor is available for your specific variant.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP/Djvu: The primary tool for potential decryption.
    • Data Recovery Software: Tools like PhotoRec, Recuva, or Disk Drill can sometimes recover older, unencrypted versions of files or remnants if the ransomware did not securely delete the original files before encryption. This is a long shot.
    • Shadow Explorer: If Shadow Volume Copies were not deleted by the ransomware (which Djvu often does using vssadmin.exe delete shadows /all /quiet), tools like Shadow Explorer might help recover previous file versions.
    • Operating System and Software Patches: Keep your OS and all applications updated to prevent future infections.

4. Other Critical Information

  • Additional Precautions:
    • Information Stealers: A significant characteristic of many STOP/Djvu variants, including the [email protected]@bigmir.net variant, is that they often deploy additional malware alongside the ransomware. This commonly includes information-stealing Trojans (e.g., Vidar, Azorult, RedLine Stealer) that aim to steal browser data, cryptocurrency wallets, system information, login credentials, and other sensitive personal data. Therefore, a full system format and reinstallation are highly recommended after a Djvu infection, even if you manage to decrypt files, to ensure no backdoors or info-stealers remain.
    • Fake Decryptors: Be extremely wary of websites offering “free” decryptors for ransomware. Many are scams designed to install more malware or trick you into paying. Always rely on trusted cybersecurity vendors like Emsisoft, No More Ransom project, or reputable antivirus companies.
    • Ransom Note: The ransomware typically drops a _readme.txt file in every encrypted folder and on the desktop. This file contains instructions for contacting the attackers (usually via email) and demanding payment, often in Bitcoin. The email addresses specified (e.g., [email protected], [email protected]) and the ransom amount (typically $490 to $980) are consistent across Djvu variants.
  • Broader Impact:
    • Individual & Small Business Focus: STOP/Djvu primarily targets home users and small to medium-sized businesses (SMBs) rather than large enterprises. This is due to its reliance on less sophisticated attack vectors like pirated software.
    • High Volume, Persistent Threat: It is one of the most widespread ransomware families due to its continuous release of new variants and effective distribution methods.
    • Significant Data Loss: For victims without backups or access to a decryptor, the infection results in permanent loss of encrypted files, leading to significant financial and emotional distress.
    • Cryptocurrency Demand: Payments are almost exclusively demanded in cryptocurrency (usually Bitcoin), making them difficult to trace and recover.
    • No Guarantees of Decryption After Payment: Even if a victim pays the ransom, there is no guarantee that the attackers will provide a working decryptor. Law enforcement agencies strongly advise against paying ransoms.

Combating *[email protected]*[email protected] requires a multi-layered approach emphasizing prevention, thorough removal, and realistic expectations regarding file decryption. Regular backups remain the most effective defense against the devastating impact of ransomware.