Detect New Open S3 buckets
Description
This search looks for AWS CloudTrail events where a user has created an open/public S3 bucket.
- Type: TTP
-
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-07-19
- Author: Bhavin Patel, Patrick Bareiss, Splunk
- ID: 2a9b80d3-6340-4345-b5ad-290bf3d0dac4
Annotations
Kill Chain Phase
- Actions on Objectives
NIST
- PR.DS
- PR.AC
- DE.CM
CIS20
- CIS 13
CVE
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`cloudtrail` eventSource=s3.amazonaws.com eventName=PutBucketAcl
| rex field=_raw "(?<json_field>{.+})"
| spath input=json_field output=grantees path=requestParameters.AccessControlPolicy.AccessControlList.Grant{}
| search grantees=*
| mvexpand grantees
| spath input=grantees output=uri path=Grantee.URI
| spath input=grantees output=permission path=Permission
| search uri IN ("http://acs.amazonaws.com/groups/global/AllUsers","http://acs.amazonaws.com/groups/global/AuthenticatedUsers")
| search permission IN ("READ","READ_ACP","WRITE","WRITE_ACP","FULL_CONTROL")
| rename requestParameters.bucketName AS bucketName
| stats count min(_time) as firstTime max(_time) as lastTime by user_arn userIdentity.principalId userAgent uri permission bucketName
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `detect_new_open_s3_buckets_filter`
Macros
The SPL above uses the following Macros:
detect_new_open_s3_buckets_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required fields
List of fields required to use this analytic.
- _time
- eventSource
- eventName
- requestParameters.bucketName
- user_arn
- userIdentity.principalId
- userAgent
- uri
- permission
How To Implement
You must install the AWS App for Splunk.
Known False Positives
While this search has no known false positives, it is possible that an AWS admin has legitimately created a public bucket for a specific purpose. That said, AWS strongly advises against granting full control to the "All Users" group.
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
48.0 | 60 | 80 | User $user_arn$ has created an open/public bucket $bucketName$ with the following permissions $permission$ |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
Reference
Test Dataset
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
source | version: 3