AWS IAM S3Browser Templated S3 Bucket Policy Creation

calendar Oct 23, 2025 · attack.execution attack.t1059.009 attack.persistence attack.defense-evasion attack.initial-access attack.privilege-escalation attack.t1078.004  ·
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Detects S3 browser utility creating Inline IAM policy containing default S3 bucket name placeholder value of "".

Sigma rule (View on GitHub)

 1title: AWS IAM S3Browser Templated S3 Bucket Policy Creation
 2id: db014773-7375-4f4e-b83b-133337c0ffee
 3status: test
 4description: Detects S3 browser utility creating Inline IAM policy containing default S3 bucket name placeholder value of "<YOUR-BUCKET-NAME>".
 5references:
 6    - https://permiso.io/blog/s/unmasking-guivil-new-cloud-threat-actor
 7author: daniel.bohannon@permiso.io (@danielhbohannon)
 8date: 2023-05-17
 9tags:
10    - attack.execution
11    - attack.t1059.009
12    - attack.persistence
13    - attack.defense-evasion
14    - attack.initial-access
15    - attack.privilege-escalation
16    - attack.t1078.004
17logsource:
18    product: aws
19    service: cloudtrail
20detection:
21    selection:
22        eventSource: iam.amazonaws.com
23        eventName: PutUserPolicy
24        userAgent|contains: 'S3 Browser'
25        requestParameters|contains|all:
26            - '"arn:aws:s3:::<YOUR-BUCKET-NAME>/*"'
27            - '"s3:GetObject"'
28            - '"Allow"'
29    condition: selection
30falsepositives:
31    - Valid usage of S3 browser with accidental creation of default Inline IAM policy without changing default S3 bucket name placeholder value
32level: high

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