*_rsa

[Content by Gemini 2.5]

This detailed resource is designed to equip individuals and organizations with critical information about the ransomware variant identified by the file extension *_rsa, often associated with the Dharma ransomware family. Understanding its technical characteristics and implementing robust recovery strategies are paramount to mitigating its impact.

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The _rsa string is typically appended to encrypted files, often appearing as a new file extension or as a suffix within a longer, new extension. For example, a file named document.docx might be renamed to document.docx.id-[random_id].[email_address]._rsa or document.docx._rsa. The specific format can vary between iterations, but the _rsa string is a consistent identifier. In some cases, the ransomware appends a unique ID and an attacker’s email address before the final _rsa extension, e.g., filename.ext.id-1E857C4F.[[email protected]]._rsa.
  • Renaming Convention: The general pattern involves appending a unique ID, potentially an attacker’s email address, and then the _rsa suffix to the original filename. This makes it immediately obvious which files have been encrypted and often provides a direct communication channel (the email) for the attackers.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The _rsa variant emerged as part of the broader Dharma ransomware family (also known as Dharma/Gop). Dharma itself has been actively observed since at least late 2016/early 2017, evolving through numerous iterations with different file extensions (e.g., .dharma, .cesar, .wallet, .arena, .bip, .adobe, .combo, .america, and later .gop, .java, .bgt, .btc, .gamma, .mkp, .onion, .adame, .AUF, .heets, .waifu, and the _rsa variants). The _rsa specific variants gained prominence in 2018-2019 and continue to be observed in campaigns today.

3. Primary Attack Vectors

  • Propagation Mechanisms: *_rsa ransomware, like other Dharma variants, primarily relies on:
    • Remote Desktop Protocol (RDP) Exploits: This is the most common and significant vector. Attackers scan for open RDP ports, then use brute-force attacks or stolen/weak credentials to gain unauthorized access to systems. Once inside, they manually deploy the ransomware.
    • Phishing Campaigns: Malicious emails containing infected attachments (e.g., weaponized Office documents, ZIP archives with executables) or links to malicious websites that download the ransomware.
    • Exploitation of Software Vulnerabilities: While less frequent than RDP, vulnerabilities in publicly accessible services, unpatched software, or insecure configurations can be exploited to gain initial access.
    • Supply Chain Attacks: In rarer cases, compromised legitimate software updates or third-party services could be used to distribute the malware.
    • Weak Credentials: Compromised or easily guessable passwords for network services, VPNs, or administrator accounts provide an entry point.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    1. Harden RDP: Disable RDP if not strictly necessary. If required, restrict access to specific IP addresses, use strong, unique passwords for RDP accounts, implement Multi-Factor Authentication (MFA), and monitor RDP logs for unusual activity. Place RDP behind a VPN.
    2. Regular Backups: Implement a 3-2-1 backup strategy: at least 3 copies of data, stored on 2 different media types, with 1 copy off-site or air-gapped. Test backups regularly.
    3. Patch Management: Keep all operating systems, software, and firmware updated with the latest security patches. Prioritize patches for known vulnerabilities, especially those affecting internet-facing services.
    4. Strong Passwords & MFA: Enforce strong, complex passwords for all user and service accounts. Implement MFA wherever possible, especially for administrative accounts and VPN access.
    5. Network Segmentation: Isolate critical systems and sensitive data from the rest of the network to limit lateral movement in case of a breach.
    6. Endpoint Detection and Response (EDR)/Antivirus: Deploy reputable antivirus and EDR solutions on all endpoints and servers, and ensure they are kept up-to-date.
    7. Email Security: Implement robust email filtering solutions to detect and block phishing attempts and malicious attachments. Educate users about identifying phishing emails.
    8. Least Privilege Principle: Grant users and applications only the minimum necessary permissions to perform their tasks.

2. Removal

  • Infection Cleanup:
    1. Isolate Infected Systems: Immediately disconnect infected computers from the network (unplug network cables, disable Wi-Fi) to prevent further spread.
    2. Identify and Contain: Determine the scope of the infection. Identify all affected systems and data.
    3. Boot into Safe Mode: For infected workstations, boot into Safe Mode with Networking (if necessary for updates or downloads) to prevent the ransomware from actively running and interfering with removal tools.
    4. Scan and Remove: Use a reputable, updated antivirus/anti-malware suite (e.g., Windows Defender, Malwarebytes, ESET, Sophos, CrowdStrike) to perform a full system scan and remove all detected ransomware components. Consider using multiple scanners for thoroughness.
    5. Remove Persistence Mechanisms: Check common ransomware persistence locations (e.g., Windows Registry Run keys, Startup folders, Scheduled Tasks) and remove any malicious entries.
    6. Change Credentials: Change all passwords for user accounts, especially administrative accounts, as they might have been compromised during the initial breach.
    7. Rebuild if Necessary: For critical systems or deeply compromised machines, a complete reformat and reinstallation of the operating system is often the safest approach to ensure complete removal.

3. File Decryption & Recovery

  • Recovery Feasibility: As of current knowledge, *_rsa variants of Dharma ransomware are generally not decryptable without the attackers’ private key. The encryption used is strong (typically AES-256 for files and RSA-2048 for the AES key encryption).
    • While some older Dharma variants had vulnerabilities that allowed for free decryption tools, the *_rsa iterations have proven resistant to public decryption efforts.
    • NoMoreRansom.org is the primary resource for publicly available decryptors. Regularly check their website, as new tools may become available if a vulnerability is found or law enforcement seizes keys. However, for *_rsa, the chances are low.
  • Essential Tools/Patches:
    • Backup Solutions: Reliable, tested backups are the most effective recovery method.
    • Shadow Explorer: If Shadow Volume Copies were not deleted by the ransomware, tools like Shadow Explorer might help recover previous versions of files. However, Dharma variants often attempt to delete these.
    • File Recovery Software: Data recovery software (e.g., PhotoRec, Recuva) might occasionally recover unencrypted fragments of files, but this is highly unreliable for complete file restoration after strong encryption.
    • Operating System Patches: Ensure all Windows updates, especially security patches for RDP vulnerabilities, are applied.
    • Endpoint Protection: Up-to-date antivirus/EDR solutions are crucial for both prevention and post-infection scanning.

4. Other Critical Information

  • Additional Precautions & Unique Characteristics:
    • Human-Operated (Hands-on Keyboard): Unlike fully automated worms, Dharma *_rsa attacks often involve human operators who gain initial access (primarily via RDP), then manually deploy and execute the ransomware, often escalating privileges and moving laterally within the network before encryption. This makes them more adaptive and harder to detect solely by signature-based tools.
    • Targeting Specific Servers: There’s a strong focus on targeting servers, especially those exposed to the internet via RDP.
    • Persistent Ransom Notes: Ransom notes (commonly INFO.txt, FILES ENCRYPTED.txt, or README.txt) are usually placed in every encrypted folder and on the desktop, providing instructions and attacker contact details (email addresses).
    • No Payment Recommendation: Law enforcement agencies and cybersecurity experts strongly advise against paying the ransom. There’s no guarantee of decryption, and it perpetuates the ransomware ecosystem.
  • Broader Impact:
    • Significant Business Disruption: *_rsa ransomware campaigns have severely impacted businesses of all sizes, leading to costly downtime, loss of critical data, and significant financial losses due even if the ransom is not paid (due to recovery efforts).
    • Evolutionary Threat: The Dharma family, including *_rsa variants, is constantly evolving, with new obfuscation techniques and minor changes to evade detection and maintain effectiveness. This requires continuous vigilance and adaptation of security measures.
    • Data Loss: Without robust backups or a rare decryption key, data encrypted by *_rsa is often permanently lost, which can be catastrophic for organizations.
    • Supply Chain Risk: As RDP is often used for remote IT management, a compromise via *_rsa can sometimes cascade to managed service providers (MSPs) or their clients, highlighting the interconnected nature of cyber risk.

This comprehensive guide should serve as a vital resource for understanding, preventing, and recovering from the *_rsa ransomware threat. Stay vigilant and prioritize proactive security measures.