Ransomware actors are revisiting a tactic of using TeamViewer to gain initial access to organizational endpoints and attempting to deploy encryptors, particularly leveraging the leaked LockBit ransomware builder. TeamViewer, a legitimate remote access tool widely used in the enterprise world, is favored for its simplicity and capabilities but has become a target for scammers and ransomware actors. A recent report from Huntress reveals that cybercriminals are still exploiting TeamViewer to compromise devices and deploy ransomware. The attacks involve attempting to deploy the ransomware payload using a DOS batch file and a DLL file created with the leaked LockBit 3.0 builder.
The analyzed log files show connections from the same source in both cases, suggesting a common attacker. The attackers use TeamViewer to gain access to remote desktops, dropping malicious files to execute ransomware unhindered. The report highlights two compromised endpoints, one showing active legitimate usage by employees and the other less frequently monitored, possibly making it a more attractive target. While the attack on the first endpoint succeeded but was contained, the second endpoint’s antivirus product stopped the effort, thwarting repeated payload execution attempts.
Huntress notes similarities to LockBit encryptors created using the leaked LockBit Black builder, indicating a potential connection to the LockBit ransomware gang. The attacks through TeamViewer appear to use the password-protected LockBit 3 DLL, suggesting that the threat actors are utilizing the leaked builder’s capabilities for deploying different versions of the encryptor. TeamViewer emphasizes the importance of strong security practices, such as complex passwords, two-factor authentication, allow-lists, and regular software updates to mitigate unauthorized access. The company has also published best practices for secure unattended access to enhance user security.