Importing AWS Security Hub Findings into Microsoft Sentinel

This blog explores how to ingest AWS Security Hub findings into Microsoft Sentinel using native solutions. Although a GitHub reference for deploying an Azure Function-based solution is included, my experience assisting a customer with its implementation provided valuable insights. Instead of step-by-step instructions, I’ll provide a high-level overview and guidance to navigate potential challenges. Let’s dive in! 

Ingest AWS Security Hub Events to Azure Sentinel 

https://github.com/Azure/Azure-Sentinel/blob/master/DataConnectors/AWS-SecurityHubFindings/README.md#ingest-aws-security-hub-events-to-azure-sentinel 
 
What is AWS Security Hub? 
 
AWS Security Hub is a cloud security posture management (CSPM) service that performs automated, continuous security best practice checks against your AWS resources to help you identify misconfigurations, and aggregates your security alerts (i.e. findings) in a standardized format so that you can more easily enrich, investigate, and remediate them. 

As of November 2024, we already have an S3 connector that ingests logs from specific AWS services: VPC Flow Logs, Amazon GuardDuty, CloudTrail, and CloudWatch, by pulling them from an S3 bucket. We will rely on this connector to receive findings from AWS Security Hub into the AWSCloudWatch table in Microsoft Sentinel, as these findings are sent to the CloudWatch service. While the data ingested into the  AWSCloudWatch table may not be parsed exactly as expected, a KQL transformation rule will help address this — more on that later. 

The flow would look like this

High level overview

This graphic and the following text show how the parts of the S3 connector solution interact.

• AWS services are configured to send their logs to S3 (Simple Storage Service) storage buckets. 

• The S3 bucket sends notification messages to the SQS (Simple Queue Service) message queue whenever it receives new logs. 

• The Microsoft Sentinel AWS S3 connector polls the SQS queue at regular, frequent intervals. If there is a message in the queue, it will contain the path to the log files. 

• The connector reads the message with the path, then fetches the files from the S3 bucket. 

• To connect to the SQS queue and the S3 bucket, Microsoft Sentinel uses a federated web identity provider (Microsoft Entra ID) for authenticating with AWS through OpenID Connect (OIDC), and assuming an AWS IAM role. The role is configured with a permissions policy giving it access to those resources. 

Reference https://learn.microsoft.com/en-us/azure/sentinel/connect-aws?tabs=s3#architecture-overview 

To forward findings from AWS Security Hub to CloudWatch, we will use EventBridge. 

First, we will create a CloudWatch log group to serve as the destination for these events before setting up the EventBridge rule. 

Creating a CloudWatch log group 
 
Follow the steps here for creating a CloudWatch log groups Working with log groups and log streams — Amazon CloudWatch Logs 

To be able to add a CloudWatch log group as a target in the EventBridge rule. The log group must start with /aws/events.

For reference Configuring an EventBridge rule for Security Hub findings — AWS Security Hub

Create a new EventBridge rule with event pattern 

In my example I am not filtering out any findings but if you like to filter for example based on severity like INFORMATIONAL, LOW you can update the event pattern. 

Refer here for Configuring an EventBridge rule for Security Hub findings — AWS Security Hub 

Event Pattern

Exporting logs from CloudWatch log group to S3 bucket 

Logs arriving in the CloudWatch log group are in GZIP format, which is accepted by Microsoft Sentinel. These logs can now be sent over to Sentinel. 
 
Exporting log data to Amazon S3 — Amazon CloudWatch Logs 
 
We can even automate the process which is defined here. 
 
Automate! Export of Cloudwatch Logs to S3 Bucket Using Lambda with Eventbridge Trigger — DEV Community 
 
Now we can rely on the instructions of setting up S3 Connector in Sentinel 
Connect Microsoft Sentinel to Amazon Web Services to ingest AWS service log data | Microsoft Learn 
 
We have already configured an AWS service(CloudWatch) to export logs to an S3 bucket so skip the mentioned step. 

Logs arriving in Microsoft Sentinel will appear in the AWSCloudWatch table but won't be parsed as expected. The finding is stored in the Message column. 

KQL Transformation 

We can use this KQL transformation query to parse the logs. 

AWSCloudWatch
| where isnotempty(Message) // Ensure message is not empty
| extend CleanMessage = replace_regex(Message, @"^\S+\s", "") // Remove the timestamp at the beginning
| extend ParsedMessage = parse_json(CleanMessage) // Parse the cleaned message as JSON
| where isnotempty(ParsedMessage) // Filter only rows where parsing was successful
| extend FindingsArray = ParsedMessage.detail.findings // Extract 'findings' array
| mv-expand FindingsArray // Expand findings array into rows
| extend Findings = parse_json(FindingsArray) // Parse each finding as JSON
| extend Region = tostring(ParsedMessage.region), // Extract region from the top-level message
          Severity = tostring(Findings.Severity.Label), // Extract Severity from findings
          Account = tostring(ParsedMessage.account), // Extract account from the top-level message
          Product = tostring(Findings.ProductName) // Extract Product from findings
| project Title = tostring(Findings.Title), Region, Severity, Account, Product // Extract Title, Region, Severity, Account, and Product

KQL Tranformation query for parsing AWS Security Hub findings.

Debugging Tips 
 
#1 Not able to add a CloudWatch log group as a target in the eventbridge rule. 
 
To add a CloudWatch log group as a target, you can either create a new log group or use an existing log group. The log group must start with /aws/events. 

#2 Cannot search the CloudWatch log group. 
 
Ensure that AWS service is selected in the target group. 

#3 Error enabling and configuring event notifications using the Amazon S3 console

When configuring your S3 bucket to send notification messages to your SQS queue as part of the S3 connector setup, you might encounter an issue related to the queue name. In my experience, I received an access policy error even though the queue name was visible. 

If you face a similar issue, I recommend loosening the access policy attached to the queue temporarily and testing the setup again. Once it works, you can refine the policy to meet your security requirements. 

Selecting queue name when creating event notification at the S3 bucket level

Queue access policy for testing