How to Revoke Stolen AWS IAM Credentials in Real Time During an S3 Attack

When an EC2 instance is compromised, attackers can extract temporary IAM credentials from the metadata service and begin bulk-downloading sensitive S3 data before a patch is ready. AWS GuardDuty can detect this via an Exfiltration:S3/AnomalousBehavior alert, triggering an urgent need to cut off access immediately. The fastest containment method is attaching an inline deny policy to the compromised IAM role using a timestamp condition, which invalidates all credentials issued before that moment — with no propagation delay. This approach blocks the attacker's stolen credentials across any network, while allowing the EC2 instance to automatically fetch new, valid credentials from the metadata service. Simply isolating the instance via a security group change is insufficient, as the attacker may already hold the credentials off-instance.