Detection: AWS Defense Evasion PutBucketLifecycle

Updated Date: 2024-05-28 ID: ce1c0e2b-9303-4903-818b-0d9002fc6ea4 Author: Bhavin Patel Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects PutBucketLifecycle events in AWS CloudTrail logs where a user sets a lifecycle rule for an S3 bucket with an expiration period of fewer than three days. This detection leverages CloudTrail logs to identify suspicious lifecycle configurations. This activity is significant because attackers may use it to delete CloudTrail logs quickly, thereby evading detection and impairing forensic investigations. If confirmed malicious, this could allow attackers to cover their tracks, making it difficult to trace their actions and respond to the breach effectively.

1`cloudtrail` eventName=PutBucketLifecycle user_type=IAMUser errorCode=success 
2|  spath path=requestParameters{}.LifecycleConfiguration{}.Rule{}.Expiration{}.Days output=expiration_days 
3|  spath path=requestParameters{}.bucketName output=bucket_name 
4| stats count min(_time) as firstTime max(_time) as lastTime  by src region eventName userAgent user_arn aws_account_id expiration_days  bucket_name user_type
5| `security_content_ctime(firstTime)` 
6|  `security_content_ctime(lastTime)` 
7| where expiration_days < 3 
8| `aws_defense_evasion_putbucketlifecycle_filter`

Data Source

Name Platform Sourcetype Source Supported App
AWS CloudTrail PutBucketLifecycle AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail' N/A

Macros Used

Name Value
cloudtrail sourcetype=aws:cloudtrail
aws_defense_evasion_putbucketlifecycle_filter search *
aws_defense_evasion_putbucketlifecycle_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1562.008 Disable or Modify Cloud Logs Defense Evasion
T1562 Impair Defenses Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
APT29
Magic Hound

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event False
This configuration file applies to all detections of type hunting.

Implementation

You must install Splunk AWS Add on and enable CloudTrail logs in your AWS Environment. We recommend our users to set the expiration days value according to your company's log retention policies.

Known False Positives

While this search has no known false positives, it is possible that it is a legitimate admin activity. Please consider filtering out these noisy events using userAgent, user_arn field names.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $user_arn$ has created a new rule to on an S3 bucket $bucket_name$ with short expiration days 20 50 40
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_cloudtrail aws:cloudtrail
Integration ✅ Passing Dataset aws_cloudtrail aws:cloudtrail

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: GitHub | Version: 2