This rule detects the initial access of AWS Systems Manager (SSM) SecureString parameters using the GetParameter or GetParameters API calls, specifically focusing on occurrences where the withDecryption flag is set to true. This behavior raises significant security concerns as it suggests an attempt to access sensitive data that is typically protected through encryption. The rule is triggered when it identifies an AWS resource accessing SecureStrings—parameters encrypted using a Key Management Service (KMS) key—indicating a possible move towards data exfiltration or unauthorized access. The detection mechanism utilizes AWS CloudTrail logs alongside specific attributes that signal potential misuse of credentials or permissions. False positives should be accounted for by confirming the context of the access and verifying if users have legitimate reasons for accessing sensitive parameters. Investigations should include reviewing user behaviors, geolocation data, and other related CloudTrail events to ascertain whether there is malicious intent or if the access was valid. Ensuring controls are in place for monitoring access patterns can help mitigate risks associated with improper access to encrypted information.