Threat actors utilizing the BianLian ransomware have been detected exploiting vulnerabilities in JetBrains TeamCity software, intensifying concerns about cybersecurity breaches. Security analysts, responding to recent intrusions, have identified the deployment of a PowerShell implementation of BianLian’s Go backdoor following the exploitation of a vulnerable TeamCity server. The attack chain involves leveraging CVE-2024-27198 or CVE-2023-42793 to gain initial access, subsequently enabling the execution of malicious commands for lateral movement within the environment.
BianLian, which emerged in June 2022, has shifted its focus exclusively to exfiltration-based extortion since the release of a decryptor in January 2023. The threat actors’ modus operandi includes implanting a custom backdoor tailored to each victim, alongside deploying remote desktop tools such as AnyDesk, Atera, SplashTop, and TeamViewer. In a notable shift in tactics, the threat actors have pivoted to a PowerShell implementation of their backdoor when their standard Go backdoor execution attempts failed, showcasing their adaptability and sophistication.
The PowerShell backdoor, obfuscated as “web.ps1,” is designed to establish a TCP socket for additional network communication with an actor-controlled server, enabling remote attackers to execute arbitrary actions on infected hosts. Security researchers caution about the potential post-exploitation objectives facilitated by the confirmed backdoor’s communication with the command-and-control server. Furthermore, the disclosure coincides with the revelation of proof-of-concept exploits targeting a critical security flaw in Atlassian Confluence, highlighting the persistent and evolving nature of cyber threats and the urgent need for robust cybersecurity measures.
