LoFP / it is possible to start this detection will need to be tuned by source ip or user. in addition, change the count values to an upper threshold to restrict false positives.

Techniques

• T1580

Sample rules

AWS IAM AccessDenied Discovery Events

• source: splunk
• technicques:
  • T1580

Description

The following analytic identifies excessive AccessDenied events within an hour timeframe for IAM users in AWS. It leverages AWS CloudTrail logs to detect multiple failed access attempts from the same source IP and user identity. This activity is significant as it may indicate that an access key has been compromised and is being misused for unauthorized discovery actions. If confirmed malicious, this could allow attackers to gather information about the AWS environment, potentially leading to further exploitation or privilege escalation.

Detection logic

`cloudtrail` (errorCode = "AccessDenied") user_type=IAMUser (userAgent!=*.amazonaws.com) 
| bucket _time span=1h 
| stats count as failures min(_time) as firstTime max(_time) as lastTime, dc(eventName) as methods, dc(eventSource) as sources by src_ip, userIdentity.arn, _time 
| where failures >= 5 and methods >= 1 and sources >= 1 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `aws_iam_accessdenied_discovery_events_filter`