Amazon GuardDuty: Detect Unauthorized S3 Access Automatically

Quick Answer

Amazon GuardDuty is the answer because it is a managed threat-detection service purpose-built to continuously analyze multiple AWS data sources for suspicious behavior without the security team having to build any detection logic themselves. Once S3 protection is enabled, GuardDuty can ingest S3 data events and related logs and apply its threat-intelligence and anomaly-detection models to spot patterns that indicate unauthorized or malicious activity, such as unusual access from an unfamiliar geography, requests consistent with data exfiltration, or access patterns that deviate from a bucket's normal usage, and it turns whatever it finds into a structured finding rather than raw log entries the team would have to comb through manually. The distinction that matters here is between raw log collection and actual analysis: plenty of AWS services can capture or store S3 access activity, but GuardDuty's role is specifically to interpret that activity against known threat patterns and behavioral baselines and surface only what looks suspicious, which is what lets those findings feed directly into automated remediation workflows. Whenever a scenario specifically asks for a service that can automatically analyze logs and generate findings for suspicious activity, rather than one that merely collects or stores the logs, that phrasing is pointing at a threat-detection service like GuardDuty rather than a logging or auditing service, since detection and interpretation is GuardDuty's specific job in the AWS security toolset.