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AWSCloudTrail - S3 bucket exposed via policy

Description

Detects S3 bucket policy updates that allow public principals without restrictive conditions. Public bucket policies can expose sensitive data and should be reviewed immediately.

Rule type: Scheduled
Version: 1.0.2
Declared status: Available
Query frequency: 1h
Query period: 1h
Trigger: gt 0

Declared MITRE coverage

Exfiltration T1537

Declared sources

Metadata from the source file. No dependencies inferred from KQL.

Connectors

AWS

Data types

AWSCloudTrail

KQL query

Original query, unchanged.

AWSCloudTrail
| where EventName == "PutBucketPolicy" and isempty(ErrorCode) and isempty(ErrorMessage)
| extend Statement = parse_json(tostring((parse_json(RequestParameters).bucketPolicy))).Statement
| mvexpand Statement
| extend Action = parse_json(Statement).Action , Effect = tostring(parse_json(Statement).Effect), Resource = tostring(parse_json(Statement).Resource), Condition = tostring(parse_json(Statement).Condition), Principal_aws = tostring(parse_json(Statement).Principal.AWS), Principal = tostring(parse_json(Statement).Principal)
| extend Action = tostring(Action)
| where Effect =~ "Allow" and (Principal_aws == "*" or Principal == "*") and isempty(Condition)
| extend UserIdentityArn = iif(isempty(UserIdentityArn), tostring(parse_json(Resources)[0].ARN), UserIdentityArn)
| extend UserName = tostring(split(UserIdentityArn, '/')[-1])
| extend AccountName = case( UserIdentityPrincipalid == "Anonymous", "Anonymous", isempty(UserIdentityUserName), UserName, UserIdentityUserName)
| extend AccountName = iif(AccountName contains "@", tostring(split(AccountName, '@', 0)[0]), AccountName),
  AccountUPNSuffix = iif(AccountName contains "@", tostring(split(AccountName, '@', 1)[0]), "")
| distinct TimeGenerated, EventName, SourceIpAddress, RecipientAccountId, AccountName, AccountUPNSuffix, UserIdentityArn, UserIdentityUserName

Declared entities

AccountIP

Source provenance

GitHub

Displayed values come from files in Azure/Azure-Sentinel. They describe the published template, not your workspace configuration.

File: Solutions/Amazon Web Services/Analytic Rules/AWS_S3BucketExposedviaPolicy.yaml ↗
Commit: 9800e51 ↗
Source identifier: 44a5b65e-b0a9-4591-aabc-388fd92a28c4

Additional source files 2

Solutions/Amazon Web Services/Analytic Rules/AWS_S3BucketExposedviaPolicy.yamlsource ↗Solutions/Amazon Web Services/Data/Solution_AmazonWebServices.jsonsolution-membership ↗

GSTEP / CATALOG TRACKING

Added to catalog : 16 Sept 2026 · 05:49 UTC
Last change observed : 16 Sept 2026 · 05:49 UTC

GSTEP sync dates, separate from the source content’s publication dates.