The rule 'EC2 Security Group Modified' detects modifications to AWS EC2 Security Groups by analyzing CloudTrail logs for specific event names associated with security group changes. The primary focus is on events like 'AuthorizeSecurityGroupIngress', which indicate changes to ingress rules within security groups. This detection aims to identify unauthorized modifications that may represent attempts to bypass security controls or limit security posture. The rule includes tests to validate results against expected outcomes and is intended for AWS environments, where monitoring access and changes to security groups is critical for maintaining a secure cloud infrastructure. This rule is categorized under info severity, alerting on any modification actions to ensure administrators can review potential implications without immediate alarm.