2lwnpp2b

[Content by Gemini 2.5]

This document provides a comprehensive analysis and recovery guide for the ransomware variant identified by the file extension 2lwnpp2b. This variant is a known iteration within the STOP/Djvu ransomware family, a prolific and constantly evolving threat that has plagued users for several years.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact file extension used by this ransomware variant is .2lwnpp2b.
  • Renaming Convention: The ransomware appends the .2lwnpp2b extension to encrypted files. The typical renaming pattern follows:
    original_filename.original_extension.2lwnpp2b
    For example, a file named document.docx would be renamed to document.docx.2lwnpp2b, and image.jpg would become image.jpg.2lwnpp2b. In some cases, the ransomware might also encrypt folder names or replace them with random characters, though this is less common than file encryption.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The STOP/Djvu ransomware family has been continuously active and developing new variants since late 2018. Variants utilizing specific extensions like 2lwnpp2b typically emerge as part of this ongoing evolution, often appearing in waves for a few weeks or months before new extensions are introduced. The 2lwnpp2b variant specifically was observed in late 2023 and early 2024, fitting into the continuous deployment cycle of new Djvu extensions.

3. Primary Attack Vectors

The 2lwnpp2b variant, consistent with the STOP/Djvu family, primarily relies on social engineering and deceptive tactics rather than complex exploit chains for initial access. Common propagation mechanisms include:

  • Cracked Software and Pirated Content: This is the most prevalent vector. Users attempting to download pirated software, cracked versions of legitimate applications (e.g., Adobe Photoshop, Microsoft Office, various games, VPNs), or “keygen” tools from untrusted websites are often infected. The ransomware is typically bundled within these downloads.
  • Fake Software Updates: Malicious websites or pop-ups may trick users into downloading fake software updates (e.g., for Flash Player, Java, web browsers) that secretly install the ransomware.
  • Malicious Email Attachments & Phishing Campaigns: While less common than cracked software for Djvu, some infections occur via phishing emails containing malicious attachments (e.g., seemingly legitimate documents with embedded macros, or archives containing executables) or links to compromised websites.
  • Malvertising: Malicious advertisements on legitimate or compromised websites can redirect users to landing pages that automatically download the ransomware or trick them into doing so.
  • Deceptive Download Sites: Websites pretending to offer legitimate free downloads (e.g., fonts, templates, drivers) may serve the ransomware instead.
  • USB Drives (less common): In some cases, the ransomware might spread via infected USB drives if auto-run features are enabled or users manually execute malicious files.
  • Exploitation of Vulnerabilities (Rare for Djvu): Unlike some other major ransomware families (e.g., WannaCry via EternalBlue, Ryuk via RDP brute-forcing), STOP/Djvu variants like 2lwnpp2b typically do not exploit network vulnerabilities like SMBv1 or RDP for initial compromise. Their propagation relies more on user execution of deceptive downloads. However, if a system is already compromised via RDP or other means, an attacker might manually deploy Djvu.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are crucial to prevent infection by 2lwnpp2b and similar ransomware:

  • Regular Data Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, on 2 different media, with 1 copy off-site or air-gapped). This is the single most effective defense against data loss due to ransomware.
  • Software & OS Updates: Keep your operating system, applications, and security software fully patched and up-to-date to close known vulnerabilities.
  • Reputable Antivirus/Anti-Malware: Use a comprehensive, up-to-date antivirus suite with real-time protection and behavioral detection capabilities.
  • User Education: Train users to recognize phishing attempts, avoid downloading cracked software or pirated content, and be wary of suspicious links and attachments.
  • Strong Passwords & MFA: Use strong, unique passwords for all accounts and enable multi-factor authentication (MFA) wherever possible, especially for critical services.
  • Network Segmentation: Isolate critical systems and sensitive data from the rest of the network to limit lateral movement in case of a breach.
  • Firewall Configuration: Configure firewalls to block unauthorized inbound and outbound connections.
  • Disable Unnecessary Services: Turn off services like SMBv1 and RDP if not strictly needed, or secure them rigorously.

2. Removal

Removing the 2lwnpp2b ransomware executable from an infected system is a critical first step, but it does not decrypt your files.

  • Isolate the Infected System: Immediately disconnect the infected computer from the network (both wired and Wi-Fi) to prevent further spread.
  • Boot into Safe Mode: Restart your computer and boot into Safe Mode with Networking. This loads only essential services, often preventing the ransomware from running its full encryption routine or hindering its self-protection mechanisms.
  • Run a Full System Scan:
    • Use a reputable antivirus or anti-malware program (e.g., Malwarebytes, Windows Defender, Emsisoft Anti-Malware).
    • Ensure the security software definitions are fully updated.
    • Perform a comprehensive full system scan to detect and remove all components of the ransomware (executable files, dropped payloads, registry entries, scheduled tasks). Look for files with suspicious names in common system directories (%TEMP%, %APPDATA%, %LOCALAPPDATA%, C:\ProgramData\).
    • Pay close attention to any detection of companion malware, as STOP/Djvu often drops information stealers like Vidar or Azorult. These must also be fully removed.
  • Check Startup Items and Scheduled Tasks: Manually inspect startup folders (shell:startup, shell:common startup), Task Scheduler, and Registry Run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run, HKLM\Software\Microsoft\Windows\CurrentVersion\Run) for suspicious entries that could re-launch the ransomware.
  • Delete Shadow Volume Copies: The ransomware attempts to delete Shadow Volume Copies to prevent recovery. Use vssadmin delete shadows /all /quiet via an elevated command prompt to ensure they are gone if you are not planning to recover via them, and to prevent the ransomware from re-infecting them. However, if you are attempting recovery, avoid this step initially.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption of files encrypted by 2lwnpp2b is challenging and often not possible without paying the ransom or a stroke of luck.
    • Online Keys (Most Common): Newer STOP/Djvu variants, including 2lwnpp2b, primarily use unique online encryption keys for each victim. This means the decryption key is generated on the attacker’s server and is unique to your infection. Without access to this specific key from the attackers, decryption is impossible.
    • Offline Keys (Less Common, Older Variants): In some rare cases (e.g., if the ransomware cannot connect to its C2 server during encryption), it might use a pre-determined “offline” key. If this happens, and the specific offline key for the 2lwnpp2b variant is known and publicly available, then decryption might be possible.
  • Essential Tools/Patches:
    • Emsisoft Decryptor for STOP/Djvu: This is the primary tool for attempting decryption. You can download it from the Emsisoft website.
      • How it works: The decryptor works by trying to match encrypted files with known encryption patterns and collected keys. You’ll need to provide an encrypted file and its original, unencrypted version (if available) to help the tool identify the specific key used.
      • Limitations: The decryptor’s success is highly dependent on whether an “offline” key was used or if the specific “online” key for your infection has somehow been compromised and added to their database. For most 2lwnpp2b victims (who likely have unique online keys), the decryptor will be unable to help unless the key is known. It will notify you if your files were encrypted with an “offline ID” (potentially decryptable) or an “online ID” (unlikely to be decryptable without the specific key).
    • Data Recovery Software: Tools like PhotoRec, Recuva, or Disk Drill might recover older versions of files or deleted shadow copies if the ransomware failed to completely remove them. Success rates are generally low, as Djvu is designed to securely delete originals and shadow copies.
  • Best Recovery Method: The most reliable method to recover files is from secure, isolated backups created before the infection. If you have backups, restore your system from a clean backup point after ensuring the ransomware is completely removed.

4. Other Critical Information

  • Ransom Note: 2lwnpp2b typically drops a ransom note named _readme.txt in every folder containing encrypted files, and often on the desktop. This note contains instructions for contacting the attackers (usually via email) to pay the ransom, typically demanding several hundred to over a thousand US dollars in cryptocurrency (e.g., Bitcoin).
  • Information Stealers: A significant characteristic of the STOP/Djvu family is its tendency to install information-stealing malware (e.g., Vidar, Azorult, RedLine Stealer) alongside the ransomware. These stealers are designed to pilfer sensitive data such as:
    • Browser saved passwords, cookies, autofill data
    • Cryptocurrency wallet data
    • Credit card details
    • VPN credentials
    • Files from the desktop
    • Telegram chats and other messaging app data
    • This means that even if you pay the ransom and recover your files (which is not guaranteed), your personal and financial information may already be compromised.
  • Fake Decryptors: Be extremely wary of websites offering “free” decryptors for STOP/Djvu. These are almost always scams designed to either install more malware, steal your money, or cause further damage to your files. Always rely on trusted sources like Emsisoft or official security vendor websites.
  • Broader Impact: The sheer volume of new STOP/Djvu variants constantly being released makes it one of the most persistent and widespread ransomware threats, particularly targeting individual users and small businesses through their common practice of seeking out “free” software. Its bundling with info-stealers adds a significant layer of risk, turning a data encryption event into a potential identity theft and financial fraud disaster. It underscores the critical need for vigilance regarding software sources and robust backup strategies.