PutBucketPolicy
AWS
PutBucketPolicy
Event
Applies or replaces the resource-based policy on an S3 bucket, defining who can access it and how.
Security Context
- Impairing defenses allows adversaries to operate freely by removing security controls that would otherwise detect or block their activity.
- Exfiltration through cloud services allows adversaries to extract data using legitimate APIs that may not trigger network-based alerts.
Log Source
CloudTrail
Sample Event
Adversarial — exfiltration / persistence. Draco applies a permissive bucket policy to fantasticlogs-niffler-archive allowing the adversary-controlled external account 555666661337 to s3:GetObject and s3:ListBucket on the entire bucket. This bypasses any IAM-based access controls in the prod account — a third-party with the bucket name now has read access without needing any identity in 555123456789. T1685 + T1530.
{ "eventVersion": "1.09", "userIdentity": { "type": "IAMUser", "principalId": "AIDADRAC0MALF0YBADGY", "arn": "arn:aws:iam::555123456789:user/draco", "accountId": "555123456789", "accessKeyId": "ASIADRAC0MALF0YEXAMP5", "userName": "draco", "sessionContext": { "attributes": { "creationDate": "2026-04-15T21:42:08Z", "mfaAuthenticated": "false" } } }, "eventTime": "2026-04-15T23:39:21Z", "eventSource": "s3.amazonaws.com", "eventName": "PutBucketPolicy", "awsRegion": "us-west-2", "sourceIPAddress": "203.0.113.66", "userAgent": "[aws-cli/1.18.147 Python/3.7.10 Linux/5.4.0-1045-aws botocore/1.18.6]", "requestParameters": { "bucketName": "fantasticlogs-niffler-archive", "Host": "fantasticlogs-niffler-archive.s3.us-west-2.amazonaws.com", "policy": [ "" ], "bucketPolicy": { "Version": "2012-10-17", "Statement": [ { "Sid": "AllowExternalReadAccess", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::555666661337:root" }, "Action": [ "s3:GetObject", "s3:ListBucket" ], "Resource": [ "arn:aws:s3:::fantasticlogs-niffler-archive", "arn:aws:s3:::fantasticlogs-niffler-archive/*" ] } ] } }, "responseElements": null, "requestID": "90000000-0000-4000-8000-000101100100", "eventID": "90000000-0000-4000-8000-000101100101", "readOnly": false, "resources": [ { "accountId": "555123456789", "type": "AWS::S3::Bucket", "ARN": "arn:aws:s3:::fantasticlogs-niffler-archive" } ], "eventType": "AwsApiCall", "managementEvent": true, "recipientAccountId": "555123456789", "eventCategory": "Management", "tlsDetails": { "tlsVersion": "TLSv1.3", "cipherSuite": "TLS_AES_128_GCM_SHA256", "clientProvidedHostHeader": "fantasticlogs-niffler-archive.s3.us-west-2.amazonaws.com" }}MITRE ATT&CK Mapping
Tactics: Collection Exfiltration
Techniques:
- T1530 — Data from Cloud Storage — Adversaries may access data from cloud storage.
- T1537 — Transfer Data to Cloud Account — Adversaries may exfiltrate data by transferring the data, including through sharing/syncing and creating backups of cloud environments, to another cloud account they control on the same service.