Suspicious Child Processes Spawned by JetBrains TeamCity

JetBrains TeamCity is a continuous integration and deployment server, making it a high-value target for attackers. Exploitation of TeamCity vulnerabilities can lead to remote code execution, enabling adversaries to compromise the software development pipeline. This activity is detected by monitoring for suspicious child processes initiated by the TeamCity Java executable, focusing on executables like cmd.exe, powershell.exe, and msiexec.exe. The detection logic excludes legitimate operations to reduce false positives. This activity can lead to complete compromise of the build environment, allowing attackers to inject malicious code into software builds.

Attack Chain

1. Initial Access: An attacker exploits a vulnerability (e.g., CVE-2023-42793) in the TeamCity server to gain initial access.
2. Code Execution: The attacker leverages the vulnerability to execute arbitrary code on the TeamCity server.
3. Process Spawning: The attacker spawns a command interpreter, such as cmd.exe or powershell.exe, from the TeamCity Java process (java.exe).
4. Discovery: The attacker uses discovery commands via the spawned shell to enumerate users, network configuration, and running processes using tools like whoami.exe, ipconfig.exe, and tasklist.exe.
5. Defense Evasion: The attacker leverages system binary proxy execution using tools like mshta.exe or regsvr32.exe to evade detection.
6. Persistence: While not explicitly mentioned, the attacker could establish persistence by creating scheduled tasks or modifying registry keys via spawned processes.
7. Lateral Movement: The attacker uses discovered credentials to move laterally to other systems within the network.
8. Impact: The attacker injects malicious code into software builds, compromises sensitive data, or deploys ransomware.

Impact

Successful exploitation of JetBrains TeamCity can lead to a full compromise of the software development lifecycle, resulting in supply chain attacks. Attackers can inject malicious code into software builds, leading to widespread distribution of compromised software. While specific victim counts are unavailable, this type of attack has the potential to affect numerous organizations relying on the compromised software. The Trend Micro research indicates that TeamCity vulnerability exploits can lead to Jasmin ransomware deployment.

Recommendation

• Deploy the “Suspicious JetBrains TeamCity Child Process” rule to your SIEM to detect potential exploitation attempts.
• Enable Sysmon process creation logging to capture process execution events, which are essential for triggering the detection rule.
• Review and patch any known vulnerabilities in JetBrains TeamCity, focusing on remote code execution flaws as described in the referenced Trend Micro report.
• Implement network segmentation to limit the impact of a compromised TeamCity server and prevent lateral movement.
• Continuously monitor TeamCity server logs for any unusual activity or unauthorized access attempts.
• Tune the “Suspicious JetBrains TeamCity Child Process” rule by creating exceptions for legitimate build scripts that invoke command-line utilities to reduce false positives, as mentioned in the rule’s documentation.