Attack Chain

1. Initial Access: An attacker gains initial access to a Windows system through various means such as exploiting a vulnerability or using stolen credentials.
2. Privilege Escalation: The attacker escalates privileges to gain the necessary permissions to execute system utilities.
3. Defense Evasion: The attacker uses attrib.exe to modify the hidden attribute of a malicious file or directory. For example, attrib.exe +h C:\path\to\malicious\file.exe.
4. Concealment: The malicious file or directory is now hidden from normal directory listings, making it harder for users and administrators to detect.
5. Persistence: The attacker establishes persistence by hiding malicious scripts or executables in startup directories or scheduled tasks.
6. Lateral Movement: The attacker uses the hidden files to move laterally within the network, potentially using them as part of a larger attack campaign.

Impact

The impact of this attack includes prolonged attacker presence, increased difficulty in detecting malicious activity, and potential data exfiltration or system compromise. While the risk score is relatively low, the technique contributes to a broader attack chain and can significantly hinder incident response efforts. A successful hiding of artifacts might lead to further compromise, data breaches, or ransomware deployment.

Recommendation

• Deploy the Sigma rule “Adding Hidden File Attribute via Attrib” to your SIEM to detect suspicious usage of attrib.exe.
• Enable process creation logging with command line monitoring in Windows environments to ensure the Sigma rule can capture relevant events.
• Investigate any alerts generated by the Sigma rule, focusing on the parent processes and target files to determine if the activity is legitimate.
• Correlate detections of attrib.exe with other suspicious activities or alerts on the same host.
• Implement file integrity monitoring to detect unauthorized changes to file attributes, including the hidden attribute.