| ID | Technique | Tactic |
|---|---|---|
| T1537 | Transfer Data to Cloud Account | Exfiltration |
Detection: AWS Exfiltration via Bucket Replication
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| rename requestParameters.* as *
3| stats count values(bucketName) as source_bucket values(ReplicationConfiguration.Rule.ID) as rule_id values(ReplicationConfiguration.Rule.Destination.Bucket) as destination_bucket by _time user_arn userName user_type src_ip aws_account_id userIdentity.principalId user_agent
4| `aws_exfiltration_via_bucket_replication_filter`
Data Source
| Name | Platform | Sourcetype | Source | Supported App |
|---|---|---|---|---|
| AWS CloudTrail PutBucketReplication |  AWS |
'aws:cloudtrail' |
'aws_cloudtrail' |
N/A |
Macros Used
| Name | Value |
|---|---|
| cloudtrail | sourcetype=aws:cloudtrail |
| 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
KillChainPhase.ACTIONS_ON_OBJECTIVES
NistCategory.DE_CM
Cis18Value.CIS_10
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 Notable | Yes |
| Rule Title | %name% |
| Rule Description | %description% |
| Notable Event Fields | user, dest |
| Creates Risk Event | True |
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.
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
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| AWS Bucket Replication rule $rule_id$ added on $source_bucket$ to $destination_bucket$ by user $user_arn$ from IP Address - $src_ip$ | 64 | 80 | 80 |
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