Issue with EventBridge matching CloudTrail/EC2 Event

Question

Hello,

I am having an issue where my EventBridge rule does not appear to be matching a CloudTrail log. 
The EB rule is looking for a cloudtrail log that the event name is "ReplaceRoute". An EC2 instance will make the call to update the route in the route table. Is anyone able to help or advise?
I had this working at one point and triggering and alert via SNS but since I blew away the configuration to define in Terraform I cannot get it to work/match.

***Event Pattern:***
{
  "source": ["aws.cloudtrail"],
  "detail-type": ["AWS API Call via CloudTrail"],
  "detail": {
    "eventSource": ["ec2.amazonaws.com"],
    "eventName": ["ReplaceRoute"]
  }
}

***CloudTrail Event Log Excerpt***

"eventTime": "2024-04-18T09:18:05Z",
    "eventSource": "ec2.amazonaws.com",
    "eventName": "ReplaceRoute",
    "awsRegion": "eu-west-2",
    "sourceIPAddress": "10.192.0.36",
    "requestParameters": {
        "routeTableId": "rtb-007ec00472e198134",
        "destinationCidrBlock": "0.0.0.0/0",
        "networkInterfaceId": "eni-0aea5cf0fcd11d4e9"
    },
    "responseElements": {
        "requestId": "577bde8b-fb6c-4a6f-926f-a2900d341fe9",
        "_return": true
    },
    "requestID": "577bde8b-fb6c-4a6f-926f-a2900d341fe9",
    "eventID": "567de95c-9208-4bdf-b431-f944ec1a7ff5",
    "readOnly": false,
    "eventType": "AwsApiCall",

Accepted Answer

Your almost there.. You need to monitor EC2 as the source and not cloudtrail and use this pattern as the match. I have tested and this works.
It only picks up if the IP Route Target changes and not the destination. If you want to detect if the destination changes, you need to also filter CreateRoute and DeleteRoute also.

**Event Pattern**
```
{
    "source": [
        "aws.ec2"
    ],
    "detail-type": [
        "AWS API Call via CloudTrail"
    ],
    "detail": {
        "eventSource": [
            "ec2.amazonaws.com"
        ],
        "eventName": [
            "ReplaceRoute"
        ]
    }
}
```

Side Note for terraform, instead of blowing it away, you could have imported the resource also of which it would tell you any differences from code to infrastructure

Issue with EventBridge matching CloudTrail/EC2 Event

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