63vc4

[Content by Gemini 2.5]

This resource provides a detailed breakdown of the ransomware variant identified by the file extension 63vc4, which is a known variant belonging to the extensive STOP/Djvu ransomware family.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this ransomware variant is .63vc4.
  • Renaming Convention: The ransomware typically renames encrypted files by appending the .63vc4 extension to the original filename. For example, a file named document.docx would be renamed to document.docx.63vc4. Alongside the encryption, it usually drops a ransom note file, most commonly named _readme.txt, in every folder containing encrypted files.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: STOP/Djvu ransomware, as a family, has been highly active since late 2017/early 2018. New variants, like 63vc4, are continuously released. 63vc4 itself emerged as one of the active variants within the ongoing STOP/Djvu campaign, likely appearing in late 2023 or early 2024, given the rapid turnover of new extensions within this family. This continuous evolution makes it one of the most prevalent ransomware threats impacting individual users and small businesses globally.

3. Primary Attack Vectors

STOP/Djvu variants, including 63vc4, primarily rely on distribution methods that exploit user behavior rather than sophisticated network vulnerabilities.

  • Propagation Mechanisms:
    • Bundled Software/Cracked Software: This is the most common vector. Users download “cracked” versions of legitimate software (e.g., Adobe Photoshop, Microsoft Office, video games, system optimizers) from torrent sites, free software download sites, or untrusted third-party platforms. The ransomware executable is often bundled within these installers.
    • Fake Software Updates: Malicious websites or pop-ups prompting users to install “critical” software updates (e.g., Flash Player, Java, browser updates) that are, in fact, ransomware executables.
    • Malicious Email Attachments/Phishing Campaigns: While less common for Djvu than for some other ransomware families, email attachments (e.g., seemingly legitimate invoices, shipping notifications, or resumes) containing malicious scripts or documents that download the ransomware payload upon opening.
    • Malvertising: Advertisements on legitimate or compromised websites that redirect users to malicious landing pages designed to trigger drive-by downloads or social engineering traps.
    • Fake Loaders/Downloaders: Users searching for specific software might land on sites offering a “downloader” or “loader” that, when executed, delivers the ransomware.
    • Remote Desktop Protocol (RDP) Exploits: While not a primary method for mass distribution of STOP/Djvu, poorly secured RDP endpoints can be brute-forced or compromised, allowing attackers to manually deploy the ransomware.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are the most effective defense against 63vc4 and similar ransomware variants.

  • Regular Data 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 isolated from the network to prevent encryption.
  • Reputable Antivirus/Endpoint Detection and Response (EDR): Use a high-quality antivirus solution with real-time protection and behavioral analysis capabilities. Keep it updated. EDR solutions provide more advanced threat detection and response.
  • Software Updates & Patch Management: Keep your operating system, web browsers, antivirus software, and all other applications fully updated with the latest security patches. Many ransomware attacks exploit known vulnerabilities.
  • User Education: Train users to recognize phishing attempts, avoid downloading cracked software, and be cautious about opening suspicious attachments or clicking unusual links.
  • Strong Password Policy & Multi-Factor Authentication (MFA): Especially for RDP and critical services, use strong, unique passwords and enable MFA wherever possible.
  • Network Segmentation: Isolate critical systems and sensitive data on separate network segments to limit the lateral movement of ransomware if an infection occurs.
  • Disable Unnecessary Services: Disable services like SMBv1, RDP, or PowerShell Remoting if not explicitly needed, or secure them appropriately.

2. Removal

Removing 63vc4 from an infected system is crucial to prevent further encryption or reinfection.

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi). This prevents the ransomware from spreading to other devices.
  2. Identify and Terminate Ransomware Processes:
    • Open Task Manager (Ctrl+Shift+Esc).
    • Look for suspicious processes with unusual names or high CPU/memory usage. 63vc4 often injects itself into legitimate processes or runs under obfuscated names.
    • Right-click and “End task” any suspicious processes. Be cautious, as terminating system processes can cause instability.
  3. Boot into Safe Mode: Restart the computer in Safe Mode with Networking. This often prevents the ransomware from fully loading.
  4. Scan with Anti-Malware Tools:
    • Perform a full system scan using your updated antivirus software.
    • Use reputable anti-malware scanners like Malwarebytes, HitmanPro, or Dr.Web CureIt!. Run multiple scans if possible.
    • These tools can detect and remove the ransomware executable and associated files.
  5. Remove Persistence Mechanisms: 63vc4 often creates persistence to ensure it runs on system startup.
    • Registry Editor (regedit.exe): Check HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run and HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run for suspicious entries that launch the ransomware.
    • Task Scheduler (taskschd.msc): Look for newly created tasks designed to execute the ransomware.
    • Startup Folder: Check shell:startup for suspicious shortcuts.
  6. Delete Ransomware Files: After scanning and removing persistence, locate and delete any remaining ransomware files. These are typically found in temporary folders (%TEMP%), %APPDATA%, or user profile directories.
  7. Change All Passwords: If your system was compromised, change all passwords for online accounts accessed from the infected machine (email, banking, social media, etc.).

3. File Decryption & Recovery

  • Recovery Feasibility: The possibility of decrypting files encrypted by 63vc4 depends primarily on the type of encryption key used:
    • Online Keys: Most Djvu infections, including 63vc4, use unique “online” keys for each victim. These keys are generated on the attacker’s server and are unique to your PersonalID (found in _readme.txt). Without this specific key, decryption is not possible without paying the ransom, which is generally not recommended.
    • Offline Keys: In some cases, if the ransomware fails to connect to its command-and-control server (e.g., due to network issues at the time of infection), it might use a pre-determined “offline” key. Files encrypted with offline keys can sometimes be decrypted.
  • Methods/Tools Available (if offline key):
    • Emsisoft Decryptor for STOP/Djvu: This is the primary and only legitimate tool that can decrypt files encrypted by STOP/Djvu (including 63vc4) if an offline key was used.
      • How it Works: The Emsisoft decryptor works by comparing an encrypted file with its original, unencrypted version (if available) to derive the offline key. It also uses a database of previously recovered offline keys.
      • Requirements:
        • _readme.txt file: The decryptor needs this file, which contains your PersonalID.
        • Original File (optional but highly recommended): If you have at least one pair of an encrypted file and its identical, original (unencrypted) version, the decryptor has a much higher chance of finding the key.
        • Patience: The process can be time-consuming.
    • Shadow Volume Copies (VSS): 63vc4 typically attempts to delete Shadow Volume Copies using commands like vssadmin.exe Delete Shadows /All /Quiet. However, in rare cases, this deletion might fail, or older copies might remain. You can check for previous versions of files or use tools like ShadowExplorer, but success is usually low.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP/Djvu: The go-to tool for potential decryption of offline-keyed files.
    • Reputable Anti-Malware Software: Malwarebytes, HitmanPro, Dr.Web CureIt! for removal.
    • Data Backup Solution: Essential for prevention and recovery from unrecoverable encryption.
    • Windows Updates: Keep your OS patched.

4. Other Critical Information

  • Additional Precautions:
    • Fake Decryptors: Be extremely wary of websites or tools claiming to decrypt 63vc4 files for a fee or promising instant decryption. Many are scams, malware, or simply ineffective. Stick to trusted sources like Emsisoft.
    • Information Gathering: Before attempting any recovery, collect all _readme.txt files and any PersonalID.txt or PersonalID.txt.63vc4 files (often found in C:\SystemID\). This information is vital for the Emsisoft decryptor.
    • Paying the Ransom: Cybersecurity experts and law enforcement generally advise against paying the ransom. There’s no guarantee the attackers will provide the decryption key, and it funds future criminal activities.
  • Broader Impact:
    • High Volume and Persistent Threat: STOP/Djvu, including 63vc4, is one of the most widespread ransomware families affecting individual users and small to medium-sized businesses due to its reliance on easily accessible “cracked” software distribution channels.
    • Significant Data Loss: For victims without isolated backups or who receive an online key encryption, permanent data loss is a high risk.
    • Financial Burden: Beyond ransom demands, the cost of recovery, IT services, and potential data recovery attempts can be substantial.
    • Loss of Trust and Productivity: Businesses suffer from downtime, loss of sensitive data, and reputational damage.

By understanding the technical aspects and implementing robust prevention and recovery strategies, individuals and organizations can significantly reduce their risk and mitigate the impact of 63vc4 and similar ransomware threats.