Sigma rule: AWS Bucket Block Public Access Weakened

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-e466a51ac80b, updated 2026-10-21T00:00:00.000Z.

Rule

Title
AWS Bucket Block Public Access Weakened
Status
experimental
Level
medium
Author
Shoban Chiddarth
Date
2026-10-21
File
rules/cloud/aws/cloudtrail/aws_cloudtrail_bucket_block_public_access_weakened.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the weakening of "Block Public Access" setting of S3 buckets in CloudTrail logs.
Monitoring changes to Block Public Access settings is critical, as attackers may disable these safeguards before exposing a bucket through a public ACL or bucket policy.

Log source

product
aws
service
cloudtrail

Detection

selection_event_name:
    eventSource: 's3.amazonaws.com'
    eventName: 'PutBucketPublicAccessBlock'
selection_weaken_restrict_public_buckets:
    requestParameters.PublicAccessBlockConfiguration.RestrictPublicBuckets: 'false'
selection_weaken_block_public_acls:
    requestParameters.PublicAccessBlockConfiguration.BlockPublicAcls: 'false'
selection_weaken_block_public_policy:
    requestParameters.PublicAccessBlockConfiguration.BlockPublicPolicy: 'false'
selection_weaken_ignore_public_acls:
    requestParameters.PublicAccessBlockConfiguration.IgnorePublicAcls: 'false'
selection_status_success:
    errorCode: 'Success'
selection_status_null:
    errorCode: null
condition: selection_event_name and 1 of selection_weaken_* and 1 of selection_status_*

False positives (as the rule lists them)

  • Administrators intentionally modifying Block Public Access settings to support a legitimate application or public bucket configuration.

Tags

  • attack.defense-impairment
  • attack.t1686.001

MITRE ATT&CK ids this rule names

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/cloud/aws/cloudtrail/aws_cloudtrail_bucket_block_public_access_weakened.yml

Sources and licences

  • SigmaHQ

    "AWS Bucket Block Public Access Weakened" by Shoban Chiddarth (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/cloud/aws/cloudtrail/aws_cloudtrail_bucket_block_public_access_weakened.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: AWS Bucket Block Public Access Weakened",
entity page, dataset version ref-e466a51ac80b, updated 2026-10-21T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/ab18a523-e093-4ac6-8303-8c47431f4fca (accessed 2026-11-03).
Underlying source: SigmaHQ rule ab18a523-e093-4ac6-8303-8c47431f4fca, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.