AWS S3 Delete Object Detection

AnalysisType: rule
DedupPeriodMinutes: 60
DisplayName: AWS S3 Delete Object Detection
Enabled: true
Filename: aws_s3_delete_object.py
RuleID: "AWS.S3.DeleteObject"
Threshold: 50
Severity: Info
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - S3
  - CloudTrail
Reports:
  Stratus Red Team:
    - aws.impact.s3-ransomware-batch-deletion
    - aws.impact.s3-ransomware-client-side-encryption
    - aws.impact.s3-ransomware-individual-deletion
Description: >
  This rule detects when many objects are deleted from an S3 bucket. Such actions can be indicative of unauthorized data deletion or other suspicious activities.
Runbook: |
  Investigate the user and the actions performed on the S3 bucket to ensure they were authorized. Unauthorized deletions can lead to data loss.
  Steps to investigate:
  1. Identify the user who performed the action.
  2. Verify if the action was authorized.
  3. Check for any other suspicious activities performed by the same user.
  4. If unauthorized, take necessary actions to secure the S3 bucket and prevent further unauthorized access.
Reference: https://docs.aws.amazon.com/AmazonS3/latest/userguide/delete-objects.html
Tests:
  - Name: DeleteObject
    LogType: AWS.CloudTrail
    ExpectedResult: true
    Log:
      {
        "eventVersion": "1.08",
        "userIdentity": {
          "type": "IAMUser",
          "principalId": "EXAMPLE",
          "arn": "arn:aws:iam::123456789012:user/Alice",
          "accountId": "123456789012",
          "accessKeyId": "EXAMPLEKEY",
          "userName": "Alice"
        },
        "eventTime": "2023-10-01T12:34:56Z",
        "eventSource": "s3.amazonaws.com",
        "eventName": "DeleteObject",
        "awsRegion": "us-east-1",
        "sourceIPAddress": "192.0.2.0",
        "userAgent": "aws-sdk-go/1.15.12 (go1.12.6; linux; amd64)",
        "requestParameters": {
          "bucketName": "example-bucket",
          "key": "example-object"
        },
        "responseElements": null,
        "additionalEventData": {
          "SignatureVersion": "SigV4",
          "CipherSuite": "ECDHE-RSA-AES128-GCM-SHA256",
          "bytesTransferredIn": 0,
          "bytesTransferredOut": 0
        },
        "requestID": "EXAMPLE123456789",
        "eventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "readOnly": false,
        "resources": [
          {
            "type": "AWS::S3::Object",
            "ARN": "arn:aws:s3:::example-bucket/example-object"
          }
        ],
        "eventType": "AwsApiCall",
        "managementEvent": false,
        "recipientAccountId": "123456789012",
        "sharedEventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "vpcEndpointId": "vpce-1a2b3c4d"
      }
  - Name: Other Event
    LogType: AWS.CloudTrail
    ExpectedResult: false
    Log:
      {
        "eventVersion": "1.08",
        "userIdentity": {
          "type": "IAMUser",
          "principalId": "EXAMPLE",
          "arn": "arn:aws:iam::123456789012:user/Bob",
          "accountId": "123456789012",
          "accessKeyId": "EXAMPLEKEY",
          "userName": "Bob"
        },
        "eventTime": "2023-10-01T12:34:56Z",
        "eventSource": "s3.amazonaws.com",
        "eventName": "ListBucket",
        "awsRegion": "us-east-1",
        "sourceIPAddress": "192.0.2.0",
        "userAgent": "aws-sdk-go/1.15.12 (go1.12.6; linux; amd64)",
        "requestParameters": {
          "bucketName": "example-bucket"
        },
        "responseElements": null,
        "additionalEventData": {
          "SignatureVersion": "SigV4",
          "CipherSuite": "ECDHE-RSA-AES128-GCM-SHA256",
          "bytesTransferredIn": 0,
          "bytesTransferredOut": 0
        },
        "requestID": "EXAMPLE123456789",
        "eventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "readOnly": true,
        "resources": [
          {
            "type": "AWS::S3::Bucket",
            "ARN": "arn:aws:s3:::example-bucket"
          }
        ],
        "eventType": "AwsApiCall",
        "managementEvent": false,
        "recipientAccountId": "123456789012",
        "sharedEventID": "EXAMPLE-1234-5678-9012-EXAMPLE",
        "vpcEndpointId": "vpce-1a2b3c4d"
      }