Detection: AWS Exfiltration via Bucket Replication

Updated Date: 2026-05-13 ID: eeb432d6-2212-43b6-9e89-fcd753f7da4c Author: Bhavin Patel, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects API calls to enable S3 bucket replication services. It leverages AWS CloudTrail logs to identify PutBucketReplication events, focusing on fields like bucketName, ReplicationConfiguration.Rule.Destination.Bucket, and user details. This activity is significant as it can indicate unauthorized data replication, potentially leading to data exfiltration. If confirmed malicious, attackers could replicate sensitive data to external accounts, leading to data breaches and compliance violations.

Search

 1`cloudtrail`  eventName = PutBucketReplication eventSource = s3.amazonaws.com
 2  
 3| rename user_name as user, requestParameters.ReplicationConfiguration.Rule.Destination.Bucket as bucket_name
 4  
 5| stats count min(_time) as firstTime max(_time) as lastTime
 6    BY signature dest user
 7       user_agent src vendor_account
 8       vendor_region vendor_product bucket_name
 9  
10| `security_content_ctime(firstTime)`
11  
12| `security_content_ctime(lastTime)`
13  
14| `aws_exfiltration_via_bucket_replication_filter`

Data Source

Name	Platform	Sourcetype	Source
AWS CloudTrail PutBucketReplication	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
aws_exfiltration_via_bucket_replication_filter	`search *`

aws_exfiltration_via_bucket_replication_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
T1537	Transfer Data to Cloud Account	Exfiltration

Actions on Objectives

DE.CM

CIS 10

RedCurl

Storm-0501

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

You must install splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs.

Known False Positives

It is possible that an AWS admin has legitimately implemented data replication to ensure data availability and improve data protection/backup strategies.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
AWS Bucket Replication rule added to $bucket_name$ by user $user$ from IP Address - $src$	user	user	50

Threat Objects

Field	Type
src	ip_address

References

https://hackingthe.cloud/aws/exploitation/s3-bucket-replication-exfiltration/

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: 10