Detection of Malicious AWS S3 Bucket Configuration Deletion

This threat brief focuses on the exploitation of administrative AWS S3 APIs to facilitate defense evasion and impact. Threat actors who obtain unauthorized access to AWS credentials may target S3 bucket configurations to reduce forensic visibility and inhibit data recovery. Observed actions include the successful execution of APIs such as DeleteBucketPolicy, DeleteBucketReplication, DeleteBucketCors, DeleteBucketEncryption, and DeleteBucketLifecycle.

Deleting these configurations is a high-risk activity that can expose sensitive data to public access, remove protective encryption, or prevent the automatic archival of critical logs and backups. While these operations are often performed by administrators, their execution by unfamiliar identities, from anomalous source IPs, or without documented change control constitutes a significant indicator of potential compromise. Defenders must correlate these configuration deletions with preceding or concurrent object-level activity to determine if the removal is part of a larger campaign involving data exfiltration or destructive operations.

Impact

Successful manipulation of bucket configurations results in the degradation of security posture, loss of audit trails, and potential unauthorized exposure of data. In a worst-case scenario, an adversary removes lifecycle policies to prevent retention and deletes encryption settings prior to mass data exfiltration, leaving the organization unable to reconstruct events or verify if data remained encrypted at rest during the incident.

Recommendation

• Deploy the Sigma rules below to monitor CloudTrail logs for unauthorized S3 configuration changes.
• Implement AWS Config rules (e.g., s3-bucket-policy-check, s3-bucket-logging-enabled) to provide real-time alerts for drift from organizational security baselines.
• Apply the principle of least privilege to IAM users and roles, strictly limiting access to S3 configuration-deletion APIs to known CI/CD service principals.
• Enforce multi-step approval workflows for administrative changes to critical S3 buckets containing audit logs or sensitive business data.