Description

GuardDuty is a continuous security monitoring service that analyzes and processes the following data sources: VPC Flow Logs, AWS CloudTrail event logs, and DNS logs.


Rationale: 

GuardDuty can detect compromised EC2 instances serving malware or mining bitcoin. It also monitors AWS account access behavior for signs of compromise, such as unauthorized infrastructure deployments, like instances deployed in a Region that has never been used, or unusual API calls, like a password policy change to reduce password strength.


Remediation: 

To detect unauthorized and unexpected activity in your AWS environment, GuardDuty analyzes and processes data from AWS CloudTrail event logs, VPC Flow Logs, and DNS logs. While in transit from these data sources to GuardDuty, all of the log data is encrypted. GuardDuty extracts various fields from these logs for profiling and anomaly detection, and then discards the logs.


The following sections describe the details of how GuardDuty uses each supported data source.

    AWS CloudTrail event logs

    VPC Flow Logs

    DNS logs


Reference: 

https://docs.aws.amazon.com/guardduty/latest/ug/what-is-guardduty.html