Try in Splunk Security Cloud

Description

The following analytic detects the creation of open/public S3 buckets via the AWS CLI. It leverages AWS CloudTrail logs to identify events where a user has set bucket permissions to allow access to "AuthenticatedUsers" or "AllUsers." This activity is significant because open S3 buckets can expose sensitive data to unauthorized users, leading to data breaches. If confirmed malicious, an attacker could gain unauthorized access to potentially sensitive information stored in the S3 bucket, posing a significant security risk.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-19
  • Author: Patrick Bareiss, Splunk
  • ID: 39c61d09-8b30-4154-922b-2d0a694ecc22

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1530 Data from Cloud Storage Collection
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


1
2
3
4
5
6
7



`cloudtrail` eventSource="s3.amazonaws.com" (userAgent="[aws-cli*" OR userAgent=aws-cli* ) eventName=PutBucketAcl OR requestParameters.accessControlList.x-amz-grant-read-acp IN ("*AuthenticatedUsers","*AllUsers") OR requestParameters.accessControlList.x-amz-grant-write IN ("*AuthenticatedUsers","*AllUsers") OR requestParameters.accessControlList.x-amz-grant-write-acp IN ("*AuthenticatedUsers","*AllUsers") OR requestParameters.accessControlList.x-amz-grant-full-control IN ("*AuthenticatedUsers","*AllUsers") 
| rename requestParameters.bucketName AS bucketName 
| fillnull 
| stats count min(_time) as firstTime max(_time) as lastTime by userIdentity.userName userIdentity.principalId userAgent bucketName requestParameters.accessControlList.x-amz-grant-read requestParameters.accessControlList.x-amz-grant-read-acp requestParameters.accessControlList.x-amz-grant-write requestParameters.accessControlList.x-amz-grant-write-acp requestParameters.accessControlList.x-amz-grant-full-control 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` 
| `detect_new_open_s3_buckets_over_aws_cli_filter`

Macros

The SPL above uses the following Macros:

:information_source: detect_new_open_s3_buckets_over_aws_cli_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.accessControlList.x-amz-grant-read-acp
  • requestParameters.accessControlList.x-amz-grant-write
  • requestParameters.accessControlList.x-amz-grant-write-acp
  • requestParameters.accessControlList.x-amz-grant-full-control
  • requestParameters.bucketName
  • userIdentity.userName
  • userIdentity.principalId
  • userAgent
  • bucketName

How To Implement

The Splunk AWS Add-on and Splunk App for AWS is required to utilize this data. The search requires AWS Cloudtrail logs.

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 $userIdentity.userName$ has created an open/public bucket $bucketName$ using AWS CLI with the following permissions - $requestParameters.accessControlList.x-amz-grant-read$ $requestParameters.accessControlList.x-amz-grant-read-acp$ $requestParameters.accessControlList.x-amz-grant-write$ $requestParameters.accessControlList.x-amz-grant-write-acp$ $requestParameters.accessControlList.x-amz-grant-full-control$

:information_source: 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