Attack Chain

1. An attacker gains initial access to a Linux system through various means, such as exploiting a vulnerability or compromising credentials.
2. The attacker uses a utility like cp, cat, or curl to access sensitive files such as /var/run/secrets/kubernetes.io/serviceaccount/token or /root/.ssh/id_rsa.
3. Auditd logs the file access event, capturing details about the process, user, and file path.
4. The detection rule identifies the suspicious process based on its name, executable path (e.g., /tmp/*), or command-line arguments.
5. The rule checks if the accessed file is in the list of sensitive identity files.
6. If both conditions are met, the rule triggers an alert, indicating potential unauthorized access to sensitive credentials.
7. The attacker exfiltrates the stolen credentials or uses them to move laterally within the network.
8. The attacker uses the stolen credentials to access cloud resources or other sensitive systems.

Impact

Successful exploitation can lead to the compromise of sensitive credentials, allowing attackers to gain unauthorized access to critical systems and data. This can result in data breaches, service disruptions, and financial losses. The targeted files contain credentials for Kubernetes clusters, cloud environments (AWS, Azure, Google Cloud), and SSH keys, potentially impacting a wide range of resources. The impact is particularly severe in environments where these credentials are used for managing critical infrastructure or accessing sensitive data.

Recommendation

• Deploy the Auditd Manager integration with the specified audit rules in the provided setup steps to monitor access to sensitive identity files on Linux systems. Ensure auditd is properly configured and running (auditctl -l) to generate the necessary logs.
• Deploy the Sigma rules provided to detect suspicious processes accessing sensitive identity files and tune them for your environment by excluding legitimate processes or users as needed.
• Investigate alerts generated by the Sigma rules, focusing on the process name, executable, parent command line, and the accessed file path to determine the legitimacy of the access.
• Review and harden file permissions on shared credential stores to prevent unauthorized access. Rotate exposed keys and tokens and invalidate cloud sessions if a compromise is suspected, as suggested in the rule’s documentation.