59d49

[Content by Gemini 2.5]

This document provides a comprehensive overview of the ransomware variant identified by the file extension 59d49, commonly recognized as a variant of the 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 .59d49.
  • Renaming Convention: Files encrypted by this variant will have the .59d49 extension appended to their original filenames. For example, a file named document.docx would be renamed to document.docx.59d49. The ransomware typically avoids renaming critical system files to prevent rendering the operating system unusable, which would hinder ransom payment. A ransom note, usually named _readme.txt, is dropped in every folder containing encrypted files.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants using the 59d49 extension are part of the prolific STOP/Djvu ransomware family, which has been actively evolving and spreading since late 2018. Specific .59d49 variants would emerge as new iterations within this ongoing campaign. The STOP/Djvu family is known for its continuous release of new extensions, making it one of the most active ransomware threats globally.

3. Primary Attack Vectors

The 59d49 variant, like other STOP/Djvu strains, primarily relies on less sophisticated but highly effective social engineering and distribution methods:

  • Software Cracks & Pirated Software: This is the most common infection vector. Users download “cracked” versions of popular software, key generators, or activators from torrent sites, free software download sites, or untrusted file-sharing platforms. The ransomware executable is often bundled within these downloads.
  • Malicious Websites & Fake Updates: Visiting compromised websites, clicking on malicious advertisements (malvertising), or falling for fake software update prompts (e.g., Flash Player updates) can lead to the download and execution of the ransomware.
  • Bundling with Other Malware: 59d49 and other STOP/Djvu variants are frequently bundled with information-stealing malware (e.g., Vidar, Azorult, RedLine Stealer). This means that in addition to encrypting files, the ransomware may also compromise sensitive data such as browser credentials, cryptocurrency wallets, and system information, which is exfiltrated to the attackers.
  • Phishing Campaigns (Less Common for this Family): While less prevalent for STOP/Djvu compared to other ransomware families, targeted phishing emails with malicious attachments or links could also be used, though it’s not their primary modus operandi.
  • Remote Desktop Protocol (RDP) Exploits: While not a primary method for the broader STOP/Djvu family, poorly secured RDP endpoints can be a vector for any threat actor, including those deploying this ransomware, if they gain access.

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 or offline). Ensure backups are isolated from the network to prevent encryption.
  • Software Updates: Keep your operating system, software, and antivirus programs up-to-date with the latest security patches. This mitigates vulnerabilities that ransomware could exploit.
  • Antivirus/Anti-Malware: Use reputable antivirus and anti-malware solutions with real-time protection and regularly scan your system.
  • User Education: Educate users about the dangers of downloading software from unofficial sources, clicking suspicious links, or opening attachments from unknown senders. Emphasize the risks of pirated software.
  • Firewall Configuration: Configure your firewall to block unauthorized inbound and outbound connections.
  • Application Whitelisting: Implement application whitelisting to prevent unauthorized executables from running.
  • Disable Unnecessary Services: Disable services like RDP if not needed, or secure them with strong, unique passwords and multi-factor authentication (MFA).

2. Removal

  • 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 systems.
  • Identify and Terminate Processes: Use Task Manager to identify and terminate any suspicious processes. While this might be difficult without advanced tools, look for processes with unusual names or high resource usage.
  • Scan with Reputable Anti-Malware: Boot the infected system into Safe Mode with Networking (if possible) or use a bootable anti-malware rescue disk. Run a full system scan with multiple reputable anti-malware tools (e.g., Malwarebytes, ESET, Bitdefender, Windows Defender). Ensure their definitions are up-to-date.
  • Remove Detected Threats: Allow the anti-malware software to quarantine or remove all detected ransomware components and associated malware (like info-stealers).
  • Check for Persistence Mechanisms: Manually check common persistence locations (e.g., Startup folders, Registry Run keys, Scheduled Tasks) for any leftover ransomware entries. However, this requires advanced technical knowledge.

3. File Decryption & Recovery

  • Recovery Feasibility: Decrypting files encrypted by 59d49 (and other STOP/Djvu variants) can be challenging.
    • Offline Keys: If the ransomware encrypted files using an “offline key” (meaning it couldn’t connect to its command-and-control server), there’s a possibility of decryption. The Emsisoft Decryptor for STOP/Djvu Ransomware is the primary tool for this. It relies on a database of previously discovered offline keys. You need to provide at least one encrypted file and its unencrypted original (or several pairs) to help the tool identify the key.
    • Online Keys: If the ransomware used an “online key” (which happens when it successfully communicates with the C2 server), decryption without the specific private key used for your infection is virtually impossible. Attackers rarely provide the key without payment.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP/Djvu Ransomware: This is the most important tool for potential decryption. Download it from Emsisoft’s official website.
    • Reputable Anti-Malware Solutions: For removal (Malwarebytes, ESET, Bitdefender, etc.).
    • Data Recovery Software (with caution): In some very rare cases, if the ransomware only partially encrypts or deletes shadow copies, data recovery software might retrieve some files, but this is highly unlikely for STOP/Djvu.
    • Windows Security Updates: Ensure Windows is fully patched. While not a direct decryption tool, it’s crucial for prevention.

4. Other Critical Information

  • Additional Precautions: 59d49 is part of a constantly evolving family. New variants with slightly altered encryption methods or distribution techniques are common. Be wary of any “free decryptor” tools offered on unofficial or suspicious websites, as they often contain malware themselves.
  • Information Stealer Co-infection: A critical characteristic of the STOP/Djvu family, including 59d49 variants, is their frequent bundling with information-stealing malware (like Vidar, Azorult, RedLine Stealer). This means that even if you manage to decrypt your files or restore from backup, your sensitive personal data (passwords, banking information, cryptocurrency wallet data, browser history) might have already been stolen. It is highly recommended to:
    • Change all critical passwords (email, banking, social media, online accounts) from an uninfected device.
    • Monitor financial accounts for suspicious activity.
    • Consider generating new cryptocurrency wallet addresses if the old ones were compromised.
  • Broader Impact: The STOP/Djvu family (including 59d49 variants) represents one of the most widespread and persistent ransomware threats, primarily targeting individual users and small businesses. Its high volume of daily infections, combined with the difficulty of decryption for online keys and the added threat of information theft, makes it a significant and ongoing cybersecurity concern. Its reliance on user negligence (pirated software, unsafe downloads) rather than complex exploits highlights the importance of basic cyber hygiene for prevention.