3674ad9f-5958-4f2a-5cb7-f0f56a8885ea

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This detailed resource addresses the ransomware variant identified by the unique file extension 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea. Based on the file extension’s format, this variant is unequivocally part of the STOP/Djvu ransomware family, one of the most prolific and continuously evolving ransomware threats. While the specific GUID 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea identifies a particular sub-variant or campaign, the core behaviors and recovery challenges align with the broader STOP/Djvu family.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by this ransomware will have the .3674ad9f-5958-4f2a-5cb7-f0f56a8885ea extension appended to their original names.
  • Renaming Convention: The ransomware encrypts target files and renames them by adding the unique identifier as an additional extension. For example:
    • document.docx becomes document.docx.3674ad9f-5958-4f2a-5cb7-f0f56a8885ea
    • image.jpg becomes image.jpg.3674ad9f-5958-4f2a-5cb7-f0f56a8885ea
    • It also typically creates a ransom note named _readme.txt in every folder containing encrypted files, and often on the desktop.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The STOP/Djvu ransomware family first emerged around late 2017/early 2018. Variants using GUIDs or similar long hexadecimal strings as extensions have been a consistent feature throughout its evolution. While 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea refers to a specific variant, it likely appeared as part of a continuous wave of STOP/Djvu updates and campaigns, indicating that this specific variant would have been active during a particular period within the ongoing activity of the larger family. STOP/Djvu remains one of the most active ransomware families.

3. Primary Attack Vectors

  • Propagation Mechanisms: STOP/Djvu ransomware, including the 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea variant, primarily relies on social engineering and deceptive tactics rather than exploiting complex network vulnerabilities directly. Common propagation methods include:
    • Bundled with Pirated Software/Cracks: This is the most prevalent vector. The ransomware executable is often disguised as legitimate software installers, game cracks, key generators, software activators, or torrent downloads for popular applications (e.g., Photoshop, Microsoft Office, Windows activators). Users downloading and executing these seemingly benign files unknowingly trigger the ransomware.
    • Phishing Campaigns: While less common than software bundling, phishing emails containing malicious attachments (e.g., seemingly legitimate invoices, shipping notifications, or resumes) or links to compromised websites can also deliver the payload.
    • Malvertising: Compromised legitimate advertising networks can redirect users to malicious landing pages that attempt drive-by downloads or social engineering tricks to get the user to execute the ransomware.
    • Fake Software Updates: Pop-ups or websites claiming to offer critical software updates (e.g., Flash Player, Java, browser updates) that, when clicked, download and execute the ransomware.
    • Remote Desktop Protocol (RDP) Exploits: In some cases, weak or exposed RDP credentials can be brute-forced, allowing attackers to gain access to a system and manually deploy the ransomware. This is less common for Djvu’s primary distribution, but possible.

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, with 1 off-site/offline). This is the most critical defense.
    • Software and OS Updates: Keep your operating system, web browsers, antivirus software, and all other applications fully patched and up-to-date to protect against known vulnerabilities.
    • Reputable Antivirus/Anti-Malware Software: Use a comprehensive, up-to-date security solution with real-time protection and behavioral analysis capabilities.
    • User Education: Train users to identify and avoid suspicious emails, unsolicited attachments, and questionable software downloads. Emphasize the dangers of pirated software.
    • Strong Passwords & MFA: Use strong, unique passwords for all accounts and enable Multi-Factor Authentication (MFA) wherever possible.
    • Network Segmentation: Isolate critical systems and data on separate network segments to limit lateral movement in case of an infection.
    • Disable Unnecessary Services: Turn off RDP if not needed, and ensure secure configurations if it is. Disable SMBv1.
    • Application Whitelisting: Consider implementing application whitelisting to prevent unauthorized executables (like ransomware) from running.

2. Removal

  • Infection Cleanup: The goal is to remove the ransomware executable and any associated malicious files 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) to prevent the ransomware from spreading to other devices.
    2. Identify Ransomware Files: The ransomware often drops its executable in common user directories (e.g., %APPDATA%, %TEMP%) and may create scheduled tasks for persistence.
    3. Boot into Safe Mode: Restart the computer in Safe Mode with Networking (or just Safe Mode if network access isn’t needed for tools) to prevent the ransomware from fully executing. This allows security software to run more effectively.
    4. Run Full System Scans: Perform a comprehensive scan with your updated antivirus/anti-malware software. Consider using multiple reputable scanners (e.g., Malwarebytes, HitmanPro) for thoroughness.
    5. Remove Scheduled Tasks & Persistence: Check Task Scheduler, Startup folders, and registry run keys for any entries created by the ransomware. Remove them.
    6. Delete Shadow Copies: The ransomware often attempts to delete Volume Shadow Copies to prevent easy restoration. While this often fails if the ransomware is stopped mid-way, it’s good practice to verify. Commands like vssadmin delete shadows /all /quiet (though primarily used by the ransomware, you’d want to ensure they weren’t successfully deleted by the ransomware, and then try to recover from existing ones if possible before cleanup).
    7. Change All Passwords: Assume any passwords on the compromised machine or network might be exposed. Change all user and administrator passwords, especially for accounts with network access.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Decryption is Challenging: For STOP/Djvu variants like 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea, decryption without the criminals’ private key is highly challenging, and often impossible for “online” keys.
    • Online vs. Offline Keys: STOP/Djvu uses a mechanism where it attempts to contact its Command and Control (C2) server to generate a unique “online” key for encryption. If it succeeds, the chances of free decryption are extremely low. If it fails to connect (e.g., due to network issues, C2 server downtime, or a security product blocking connection), it falls back to an “offline” key from its local database. Decryption for some offline keys might be possible if security researchers have managed to obtain and publish these keys.
    • Emsisoft Decryptor: Emsisoft, in collaboration with the No More Ransom project, frequently updates its free decryptor for STOP/Djvu ransomware. This is the primary hope for decryption. You will need at least one encrypted file and its original, unencrypted version (if possible) for the tool to work its magic. Even if you don’t have the original, the tool can sometimes identify if an offline key was used.
    • No More Ransom Project: Always check the No More Ransom website (www.nomoreransom.org) for updated decryptors and advice. They are the central hub for ransomware decryption tools.
    • Paying the Ransom (Discouraged): Cybersecurity experts universally advise against paying the ransom. There is no guarantee you will receive a decryptor, and it fuels the criminal ecosystem.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP Djvu: This is the most crucial tool for potential file recovery. Download it only from official sources like Emsisoft’s website or No More Ransom.
    • Reputable Anti-Malware Software: Malwarebytes, HitmanPro, ESET, Bitdefender, etc., for removal.
    • Windows Security Updates: Ensure your Windows OS is fully patched.
    • Data Recovery Software: In rare cases, if only headers or parts of files were encrypted, or if the ransomware failed to delete shadow copies effectively, data recovery tools might salvage some data, but this is generally not reliable for fully encrypted files.

4. Other Critical Information

  • Additional Precautions:
    • Ransom Note Analysis: The _readme.txt ransom note is critical. It typically contains the attacker’s email addresses for contact and instructions. Do NOT delete this note until you have fully assessed your recovery options. It might also contain a “personal ID” or “user ID” that helps in identifying the specific encryption key used.
    • System File Modification: STOP/Djvu often modifies the Windows hosts file (C:\Windows\System32\drivers\etc\hosts) to block access to security-related websites, making it harder for victims to seek help or download security tools. Check and restore this file to its default state.
  • Broader Impact:
    • Widespread Impact on Individuals and SMBs: STOP/Djvu, due to its distribution via pirated software, disproportionately affects individual users and small to medium-sized businesses who might not have sophisticated security measures or robust backup strategies.
    • Significant Data Loss: Given the high difficulty of decrypting files encrypted with “online” keys, victims often face permanent data loss if they do not have backups.
    • Persistence and Evasion: The STOP/Djvu family is constantly updated with new variants, making detection and decryption an ongoing cat-and-mouse game for security researchers. Its reliance on user-initiated execution (via pirated software) makes traditional network perimeter defenses less effective.
    • Profitability Model: The high volume of infections, even with a low percentage of paid ransoms, makes this family highly profitable for the attackers, ensuring its continued development and proliferation.

Combating 3674ad9f-5958-4f2a-5cb7-f0f56a8885ea effectively requires a combination of robust preventative measures and a clear understanding of the limited recovery options available once an infection occurs. Prioritizing offline backups and user education remains your strongest defense.