AWS Exfiltration via Bucket Replication

name: AWS Exfiltration via Bucket Replication
id: eeb432d6-2212-43b6-9e89-fcd753f7da4c
version: 8
date: '2026-03-10'
author: Bhavin Patel, Splunk
status: production
type: TTP
data_source:
    - AWS CloudTrail PutBucketReplication
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: |-
    `cloudtrail`  eventName = PutBucketReplication eventSource = s3.amazonaws.com
      | rename user_name as user, requestParameters.ReplicationConfiguration.Rule.Destination.Bucket as bucket_name
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY signature dest user
           user_agent src vendor_account
           vendor_region vendor_product bucket_name
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `aws_exfiltration_via_bucket_replication_filter`
how_to_implement: 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.
references:
    - https://hackingthe.cloud/aws/exploitation/s3-bucket-replication-exfiltration/
drilldown_searches:
    - name: View the detection results for - "$user_arn$" and "$aws_account_id$"
      search: '%original_detection_search% | search  user_arn = "$user_arn$" aws_account_id = "$aws_account_id$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user_arn$" and "$aws_account_id$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user_arn$", "$aws_account_id$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: AWS Bucket Replication rule added to $bucket_name$ by user $user$ from IP Address - $src$
    risk_objects:
        - field: user
          type: user
          score: 50
    threat_objects:
        - field: src
          type: ip_address
tags:
    analytic_story:
        - Suspicious AWS S3 Activities
        - Data Exfiltration
    asset_type: EC2 Snapshot
    mitre_attack_id:
        - T1537
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1119/aws_exfil_datasync/cloudtrail.json
          sourcetype: aws:cloudtrail
          source: aws_cloudtrail