What Is Amazon GuardDuty?

Amazon 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. It uses threat intelligence feeds, such as lists of malicious IPs and domains, and machine learning to identify unexpected and potentially unauthorized and malicious activity within your AWS environment. This can include issues like escalations of privileges, uses of exposed credentials, or communication with malicious IPs, URLs, or domains. For example, 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.

GuardDuty informs you of the status of your AWS environment by producing security findings that you can view in the GuardDuty console or through Amazon CloudWatch events.

How Amazon GuardDuty Uses Its Data Sources

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. The logs from these data sources are stored in the Amazon S3 buckets. GuardDuty accesses them there using the HTTPS protocol. 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

AWS CloudTrail provides you with a history of AWS API calls for your account, including API calls made using the AWS Management Console, the AWS SDKs, the command line tools, and higher-level AWS services. CloudTrail also allows you to identify which users and accounts called AWS APIs for services that support CloudTrail, the source IP address that the calls were made from, and when the calls occurred. For more information, see What is AWS CloudTrail?

You can configure CloudTrail trails to log management events and/or data events. Management events provide insight into management operations that are performed on resources in your AWS account. For example, configuring security (IAM AttachRolePolicy API operations), registering devices (Amazon EC2 CreateDefaultVpc API operations), configuring rules for routing data (Amazon EC2 CreateSubnet API operations), or setting up logging (AWS CloudTrail CreateTrail API operations). Data events provide insight into the resource operations performed on or within a resource. For example, Amazon S3 object-level API activity (GetObject, DeleteObject, and PutObject API operations) or AWS Lambda function execution activity (the Invoke API). For more information, see Logging Data and Management Events for Trails.

Currently, GuardDuty only analyzes CloudTrail management events. If you have CloudTrail configured to log data events, there will be a difference between GuardDuty analysis based on CloudTrail data and the logs that CloudTrail itself is delivering.

Another important detail about GuardDuty’s usage of CloudTrail as a data source is the handling and processing of CloudTrail’s global events. For most services, events are recorded in the region where the action occurred. For global services such as AWS IAM, AWS STS, Amazon CloudFront, and Route 53, events are delivered to any trail that includes global services, and are logged as occurring in US East (N. Virginia) Region. For more information, see About Global Service Events.

GuardDuty processes all events that come into a region, including global events that CloudTrail sends to all regions. This allows GuardDuty to maintain user and role profiles in each region and enables it to accurately detect credentials that are being maliciously used across regions.

VPC Flow Logs

VPC Flow Logs capture information about the IP traffic going to and from Amazon EC2 network interfaces in your VPC. For more information, see VPC Flow Logs.

DNS logs

If you use AWS DNS resolvers for your EC2 instances (the default setting), then GuardDuty can access and process your request and response DNS logs through the internal AWS DNS resolvers. If you are using a 3rd party DNS resolver, for example, OpenDNS or GoogleDNS, or if you set up your own DNS resolvers, then GuardDuty cannot access and process data from this data source.

Pricing for GuardDuty

For information about GuardDuty pricing, see Amazon GuardDuty Pricing.

Accessing GuardDuty

You can work with GuardDuty in any of the following ways: