*.sell

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This document provides a comprehensive overview of the ransomware variant identified by the file extension *.sell, encompassing its technical characteristics and actionable recovery strategies.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware variant discussed here is identified by its use of the .sell file extension, which it appends to encrypted files.
  • Renaming Convention: Upon successful encryption, the ransomware typically renames files following a pattern that includes the original filename, its original extension, and the appended .sell extension. For example:
    • document.docx might become document.docx.sell
    • photo.jpg might become photo.jpg.sell
    • In some instances, the filename might also include a unique victim ID or an email address for contact before the .sell extension (e.g., filename.docx.id-[victimID].[email].sell). This pattern is often observed with variants of ransomware families like Dharma or GlobeImposter, which frequently adopt custom extensions.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Variants using the .sell extension have been observed in the wild since at least 2019-2020, with continued sporadic campaigns reported throughout 2021-2023. It’s not attributed to a single, standalone ransomware family but rather is an extension frequently adopted by different ransomware groups, particularly those operating under the Ransomware-as-a-Service (RaaS) model. Notable associations include certain Dharma and GlobeImposter variants, which are known to use a wide array of custom extensions depending on the campaign.

3. Primary Attack Vectors

The *.sell ransomware, like many others operating under RaaS, leverages common and effective propagation mechanisms:

  • Remote Desktop Protocol (RDP) Exploitation: A highly favored vector. Attackers scan for open RDP ports, brute-force weak credentials, or exploit known vulnerabilities in RDP services to gain initial access to networks. Once inside, they elevate privileges and deploy the ransomware.
  • Phishing Campaigns:
    • Malicious Attachments: Emails containing seemingly legitimate but malicious attachments (e.g., weaponized Microsoft Office documents with macros, fake invoices, or shipping notifications) are a common delivery method.
    • Malicious Links: Links embedded in emails that direct users to compromised websites hosting exploit kits, or to download malicious executables disguised as legitimate software.
  • Software Vulnerabilities: Exploiting unpatched vulnerabilities in public-facing applications (e.g., web servers, VPNs, content management systems like WordPress) or network devices.
  • Software Cracks/Pirated Software: Users downloading pirated software, key generators, or crack tools from untrusted sources often inadvertently execute the ransomware bundled within these files.
  • Drive-by Downloads: Visiting compromised or malicious websites that automatically download malware without user interaction, often exploiting browser or plugin vulnerabilities.
  • Supply Chain Attacks: Although less common for individual .sell campaigns, broader supply chain compromises could theoretically distribute it through legitimate software updates or third-party components.

Remediation & Recovery Strategies:

1. Prevention

Proactive measures are the most effective defense against ransomware like *.sell:

  • Regular Data Backups: Implement a robust 3-2-1 backup strategy (3 copies of data, on 2 different media, with 1 off-site/offline copy). Ensure backups are immutable or regularly tested for restoration.
  • Patch Management: Keep operating systems, software, and firmware (especially for network devices and public-facing applications) up to date with the latest security patches.
  • Strong Password Policies & MFA: Enforce complex passwords and mandate Multi-Factor Authentication (MFA) for all user accounts, especially for RDP, VPNs, and critical systems.
  • Network Segmentation: Isolate critical systems and sensitive data on separate network segments to limit the lateral movement of ransomware.
  • Principle of Least Privilege: Grant users and applications only the minimum necessary permissions to perform their tasks.
  • Endpoint Detection and Response (EDR)/Antivirus: Deploy and maintain reputable EDR solutions or next-generation antivirus software with real-time protection and behavioral analysis capabilities.
  • User Awareness Training: Educate employees about phishing, suspicious emails, and safe browsing habits.
  • Disable/Secure RDP: If RDP is necessary, secure it with strong passwords, MFA, network-level authentication (NLA), and restrict access to trusted IPs only. Consider using a VPN for RDP access.
  • Application Whitelisting: Allow only approved applications to run on endpoints.

2. Removal

If a system is infected with *.sell ransomware, follow these steps for cleanup:

  1. Isolate the Infected System: Immediately disconnect the infected computer from the network (unplug Ethernet cable, disable Wi-Fi) to prevent further spread.
  2. Identify the Ransomware Process: Use Task Manager (Windows) or process monitoring tools to identify suspicious processes. Ransomware often runs as a high-CPU or high-disk I/O process.
  3. Boot into Safe Mode: Restart the computer in Safe Mode (with Networking, if necessary for tool downloads) to prevent the ransomware from executing its payload fully.
  4. Run a Full System Scan: Use a reputable and updated anti-malware solution (e.g., Malwarebytes, Windows Defender, ESET, Sophos) to perform a deep scan and remove all detected threats.
  5. Remove Persistence Mechanisms: Manually check common persistence locations (e.g., Registry Run keys, Startup folders, Scheduled Tasks) for any entries created by the ransomware. Tools like AutoRuns from Sysinternals can assist.
  6. Change Credentials: After ensuring the system is clean, change all passwords that might have been compromised, especially those used on the infected system or for network access.
  7. Forensic Analysis (Recommended): For organizations, conducting a forensic analysis to determine the initial compromise vector and extent of the breach is crucial for preventing future attacks.

3. File Decryption & Recovery

  • Recovery Feasibility: The possibility of decrypting files encrypted by the .sell ransomware largely depends on the specific ransomware family variant that used this extension and whether a decryption key or vulnerability has been discovered for that particular version.
    • Check No More Ransom Project: The No More Ransom initiative (www.nomoreransom.org) is the primary resource for publicly available decryptors. It is highly recommended to upload an encrypted file and the ransom note to their Crypto Sheriff tool. This tool can often identify the specific ransomware family and indicate if a free decryptor exists.
    • Specific Associations: As .sell is frequently used by Dharma and GlobeImposter variants, some older versions of these families might have decryptors available through No More Ransom or security vendor sites (e.g., Emsisoft Decryptor for Dharma, various GlobeImposter decryptors). However, newer .sell variants often remain undecryptable without the private key held by the attackers.
    • Paying the Ransom: Paying the ransom is strongly discouraged. There is no guarantee that attackers will provide a working decryptor, and it funds criminal activity.
  • Essential Tools/Patches:
    • Decryption Tools: If available, official decryptors from No More Ransom or reputable security vendors.
    • Data Recovery Software: Tools like PhotoRec or Recuva might be able to recover unencrypted shadow copies (Volume Shadow Copies Service – VSS) if the ransomware failed to delete them. However, most modern ransomware specifically targets and deletes VSS.
    • System Restore Points: Attempting to use System Restore points might revert system files but will not decrypt personal files.
    • Backups: The most reliable method for file recovery remains restoring from clean, verified backups created before the infection.

4. Other Critical Information

  • Additional Precautions:
    • Ransomware-as-a-Service (RaaS): Recognize that the .sell extension is often a characteristic of RaaS operations. This means different threat actors might use the same underlying ransomware code, potentially leading to slight variations in behavior, ransom notes, and contact methods.
    • Ransom Note Analysis: The ransom note (often info.txt, readme.txt, or similar) usually contains contact information (email address, Tox ID, Jabber ID) and payment instructions. This can sometimes help identify the specific variant or group, which is useful for forensic analysis but should not be used for contact.
    • Post-Infection Hardening: After recovery, implement a thorough hardening process, including auditing user accounts, reviewing firewall rules, and re-evaluating security configurations to prevent re-infection.
  • Broader Impact:
    • Financial Loss: Direct ransom payments (if made), costs of incident response, recovery efforts, and potential legal fees.
    • Operational Disruption: Significant downtime, loss of productivity, and inability to conduct business operations, which can last for days or weeks.
    • Data Loss: Irrecoverable loss of data if backups are not available or are also compromised.
    • Reputational Damage: Loss of customer trust, negative media coverage, and damage to brand image.
    • Legal & Regulatory Consequences: Potential fines and legal action under data protection regulations (e.g., GDPR, CCPA) if personal data is compromised.

By understanding these technical details and implementing robust recovery strategies, individuals and organizations can significantly mitigate the impact of the *.sell ransomware variant.