AWS IAM Assume Role Policy Brute Force Attempt

This alert detects potential brute force attempts on AWS IAM AssumeRole policies. While the provided source material is limited to the file's existence within a Splunk security content repository, the detection logic focuses on identifying a high volume of failed AssumeRole API calls originating from a single source IP or AWS identity within a short timeframe. Such activity could indicate an attacker attempting to discover valid roles they can assume to gain elevated privileges within an AWS environment. This activity is significant because successful role assumption grants the attacker access to resources and data associated with the assumed role, bypassing standard permission controls. A successful brute force may lead to data exfiltration, service disruption, or further lateral movement within the cloud infrastructure.

Attack Chain

1. Initial Access Attempt: An attacker attempts to gain initial access to an AWS environment, potentially through compromised credentials or an exposed API endpoint.
2. Identity Enumeration: The attacker begins enumerating available IAM roles within the AWS account to identify potential targets for privilege escalation.
3. AssumeRole Request: The attacker initiates a series of AssumeRole API calls, each targeting a different IAM role and potentially using different session names or external IDs.
4. Policy Evaluation: AWS evaluates the IAM policies associated with each role to determine if the attacker's identity is authorized to assume the role.
5. Failed Assumption Attempts: The majority of AssumeRole requests fail due to insufficient permissions or incorrect parameters, generating CloudTrail logs with error codes like AccessDenied or InvalidClientTokenId.
6. Successful Assumption (Potential): If the attacker successfully identifies a role they are authorized to assume, the AssumeRole API call returns temporary security credentials.
7. Privilege Escalation: The attacker uses the temporary security credentials to access resources and perform actions associated with the assumed role, effectively escalating their privileges.
8. Lateral Movement/Data Exfiltration: With elevated privileges, the attacker may move laterally within the AWS environment, access sensitive data, or exfiltrate information to an external location.

Impact

A successful brute force attack on AWS IAM roles can lead to significant damage. While the number of victims is unknown, the potential impact includes unauthorized access to sensitive data, compromised AWS resources, and potential disruption of cloud-based services. The attacker may be able to escalate privileges, move laterally within the AWS environment, and exfiltrate sensitive data. The targeted sectors are broad, as any organization using AWS IAM roles is potentially vulnerable.