2020

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This document provides a comprehensive overview of the ransomware variant identified by the file extension .2020. While the .2020 extension itself is generic, it has been widely observed in conjunction with various STOP/Djvu ransomware variants. This resource focuses on the characteristics and strategies applicable to ransomware exhibiting this file extension, drawing heavily from the known behaviors of STOP/Djvu.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this ransomware is .2020.
  • Renaming Convention: When a file is encrypted, its original filename is appended with the .2020 extension.
    • Example: A file named document.docx would be renamed to document.docx.2020. Similarly, image.jpg would become image.jpg.2020.
    • In some instances, particularly with STOP/Djvu variants, the ransomware might also append an additional string (often a victim ID or specific variant ID) before the .2020 extension, although the .2020 remains the final distinguishing marker.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: While the STOP/Djvu ransomware family has been active since late 2017, variants specifically employing the .2020 file extension began to be widely detected and reported in or around the year 2020. This indicates a period where this specific extension gained prominence within the ongoing campaigns of the STOP/Djvu group. The family continuously releases new variants, often with new extensions.

3. Primary Attack Vectors

The 2020 variant, like many STOP/Djvu iterations, primarily relies on social engineering and deceptive distribution methods rather than exploiting network vulnerabilities for rapid worm-like spread.

  • Propagation Mechanisms:
    • Malicious Software Cracks & Keygens: This is the most prevalent method. Users seeking pirated software (e.g., Adobe products, Microsoft Office, video games) download seemingly legitimate cracks, patches, or key generators from torrent sites or suspicious download portals. These executables are trojanized with the ransomware.
    • Fake Software Updates: Pop-ups or deceptive websites prompting users to download “critical updates” for popular software (e.g., Flash Player, Java, web browsers) can deliver the ransomware payload.
    • Malicious Advertisements (Malvertising): Clicking on compromised ads on legitimate or illicit websites can redirect users to landing pages that automatically download the ransomware or prompt a deceptive download.
    • Phishing Campaigns (Less Common for this specific variant): While traditional phishing emails are a common ransomware vector, STOP/Djvu variants are less frequently spread via direct email attachments and more via user-initiated downloads from deceptive sources. However, a phishing email could contain a link to a malicious download site.
    • Bundled Software: The ransomware might be discreetly bundled with freeware or shareware downloaded from less reputable download sites.
    • Compromised Websites: Visiting a compromised website can lead to a drive-by download or trick the user into downloading the ransomware.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Regular Data Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, on 2 different media, 1 offsite/cloud). Ensure backups are isolated from the network to prevent encryption.
    • Robust Antivirus/Endpoint Detection and Response (EDR): Keep security software up-to-date with real-time protection enabled. Consider next-generation AV/EDR solutions that use behavioral analysis.
    • Software Updates & Patching: Regularly update your operating system (Windows, macOS, Linux) and all installed applications. This closes security vulnerabilities that ransomware could exploit.
    • User Education: Train users to identify phishing attempts, suspicious links, and to be wary of downloading software from unofficial or untrusted sources (especially pirated content).
    • Firewall Configuration: Employ a strong firewall to block unauthorized inbound and outbound connections.
    • Strong Passwords & Multi-Factor Authentication (MFA): Use complex, unique passwords for all accounts and enable MFA wherever possible to secure remote access points (like RDP).
    • Disable Unnecessary Services: Turn off services like SMBv1, PowerShell Remoting, or RDP if they are not actively required, or restrict their access.
    • Principle of Least Privilege: Grant users only the minimum permissions necessary to perform their tasks.

2. Removal

  • Infection Cleanup:
    1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi). This prevents further spread to other devices on the network.
    2. Identify and Terminate Malicious Processes: Use Task Manager (Windows) or Activity Monitor (macOS) to identify suspicious processes. Look for high CPU or disk usage from unknown executables. Be cautious as legitimate system processes can be mimicked.
    3. Boot into Safe Mode: Restart the computer in Safe Mode (with Networking, if necessary, for updates/downloads) to prevent the ransomware from executing and interfering with removal tools.
    4. Full System Scan: Perform a comprehensive scan using a reputable and updated antivirus/anti-malware program (e.g., Malwarebytes, Avast, Bitdefender, ESET). Allow the software to quarantine or remove all detected threats.
    5. Check for Persistence:
      • Registry Entries: Check HKCU\Software\Microsoft\Windows\CurrentVersion\Run and HKLM\Software\Microsoft\Windows\CurrentVersion\Run for suspicious entries that launch the ransomware upon startup.
      • Scheduled Tasks: Use Task Scheduler to look for newly created or modified tasks designed to restart the ransomware.
      • Startup Folders: Check C:\Users\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup and C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup for malicious executables.
    6. Delete Malicious Files: Manually delete any identified ransomware executables or associated files, particularly from Temp or AppData folders, after the antivirus has quarantined them.
    7. Restore System Files (Optional but Recommended): Use sfc /scannow in Command Prompt (as administrator) to check for and repair corrupted Windows system files.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Often Possible (for Offline Keys): For many STOP/Djvu variants (including those using .2020), decryption is possible if the ransomware used an “offline key”. An offline key is a hardcoded decryption key used when the ransomware cannot establish contact with its command-and-control (C2) server. Security researchers often manage to extract and publish these offline keys.
    • Difficult (for Online Keys): If the ransomware successfully communicated with its C2 server and obtained a unique “online key” for the victim, decryption without paying the ransom and receiving the attacker’s key is extremely difficult, often impossible, for security researchers.
    • Emsisoft Decryptor: Emsisoft, in collaboration with security researchers, has developed a free decryptor for many STOP/Djvu variants. This tool attempts to decrypt files using known offline keys. It’s the primary recommended tool for attempting decryption for this family.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP Djvu Ransomware: Download this tool only from Emsisoft’s official website or a trusted security news source.
    • Shadow Explorer: While STOP/Djvu often attempts to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet), it’s still worth checking if they exist using Shadow Explorer or previous versions functionality in Windows. If shadow copies were not deleted, you might be able to restore some files.
    • Data Recovery Software: Tools like PhotoRec, Recuva, or EaseUS Data Recovery Wizard might recover some original, unencrypted files that were deleted before encryption, but success is limited.
    • Windows System Restore: If you have system restore points created before the infection, you might be able to revert your system state, though this won’t decrypt files already encrypted.

4. Other Critical Information

  • Additional Precautions & Unique Characteristics:

    • Ransom Note: The 2020 variant, typical of STOP/Djvu, leaves a ransom note named _readme.txt (or similar) in every folder containing encrypted files, and often on the desktop. This note provides instructions for contacting the attackers and paying the ransom.
    • Information Gathering: Before encryption, STOP/Djvu variants often attempt to collect system information and send it to the C2 server, including details about installed software, location, and a list of all encrypted files.
    • Hosts File Modification: Many STOP/Djvu variants modify the Windows hosts file (C:\Windows\System32\drivers\etc\hosts) to block access to security-related websites (e.g., antivirus vendors, security blogs) to prevent victims from seeking help or downloading removal tools. You’ll need to check and revert these changes.
    • Fake Windows Updates: The ransomware may display a fake Windows update screen during encryption to distract the user and conceal its activity.
    • No Free Decryption Promise: The ransom note explicitly states that free decryption tools are unlikely to work, trying to discourage victims from seeking help.
    • Double Extortion (Less common for this variant, but increasing trend): While STOP/Djvu primarily focuses on encryption for ransom, some modern ransomware families engage in “double extortion” (encrypting data AND exfiltrating it for public release if the ransom isn’t paid). There’s no widespread evidence of this for the 2020 variant of STOP/Djvu, but it’s a general trend to be aware of.

  • Broader Impact:

    • Widespread Individual & SMB Impact: The 2020 variant (as part of STOP/Djvu) has disproportionately affected individual users and small to medium-sized businesses (SMBs) due to its distribution methods (pirated software, fake updates).
    • Data Loss: For victims without reliable backups or unable to use decryption tools, this ransomware results in significant, often permanent, data loss.
    • Financial Strain: Paying the ransom is never guaranteed to result in decryption and funds criminal enterprises. The cost of recovery (IT services, data recovery, lost productivity) can be substantial even without paying the ransom.
    • Reputation Damage: For businesses, a ransomware attack can severely damage reputation and customer trust.