IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

« AWS S3 Bucket Server Access Logging Disabled AWS S3 Object Versioning Suspended »

› ›

AWS S3 Bucket Replicated to Another Account

edit

AWS S3 Bucket Replicated to Another Account

edit

Identifies when the PutBucketReplication operation is used to replicate S3 objects to a bucket in another AWS account. Adversaries may use bucket replication to exfiltrate sensitive data to an environment they control.

Rule type: eql

Rule indices:

filebeat-*
logs-aws.cloudtrail-*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Cloud
Data Source: AWS
Data Source: Amazon Web Services
Data Source: AWS S3
Resources: Investigation Guide
Use Case: Threat Detection
Tactic: Exfiltration

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

edit

Triage and Analysis

Investigating AWS S3 Bucket Replicated to Another Account

This rule identifies when an S3 bucket is replicated to another AWS account. While sharing bucket replication is a common practice, adversaries may exploit this feature to exfiltrate data by replicating objects to external accounts under their control.

Possible Investigation Steps

Identify the Actor: Review the aws.cloudtrail.user_identity.arn and aws.cloudtrail.user_identity.access_key_id fields to identify who made the change. Verify if this actor typically performs such actions and if they have the necessary permissions.
Review the Sharing Event: Identify the S3 bucket involved and review the event details. Look for PutBucketReplication actions where an Account key-value pair is included signifying replication to an external account.
Request and Response Parameters: Check the aws.cloudtrail.request_parameters and aws.cloudtrail.response_elements fields in the CloudTrail event to identify the role used and account ID where the bucket was replicated.
Verify the Shared Bucket: Check the S3 bucket that was replicated and its contents to determine the sensitivity of the data stored within it.
Validate External Account: Examine the AWS account to which the bucket was replicated. Determine whether this account is known and previously authorized to access such resources.
Contextualize with Recent Changes: Compare this sharing event against recent changes in S3 configurations. Look for any other recent permissions changes or unusual administrative actions.
Correlate with Other Activities: Search for related CloudTrail events before and after this change to see if the same actor or IP address engaged in other potentially suspicious activities.
Interview Relevant Personnel: If the share was initiated by a user, verify the intent and authorization for this action with the person or team responsible for managing DB backups and snapshots.

False Positive Analysis

Legitimate Backup Actions: Confirm if the S3 bucket replication aligns with scheduled backups or legitimate automation tasks.
Consistency Check: Compare the action against historical data of similar actions performed by the user or within the organization. If the action is consistent with past legitimate activities, it might indicate a false alarm.

Response and Remediation

Immediate Review and Reversal: If the change was unauthorized, update the S3 configurations to remove any unauthorized replication rules.
Enhance Monitoring and Alerts: Adjust monitoring systems to alert on similar actions, especially those involving sensitive data or permissions.
Policy Update: Review and possibly update your organization’s policies on S3 bucket/object sharing to tighten control and prevent unauthorized access.
Incident Response: If malicious intent is confirmed, consider it a data breach incident and initiate the incident response protocol. This includes further investigation, containment, and recovery.

Additional Information:

For further guidance on managing and securing S3 buckets in AWS environments, refer to the AWS S3 documentation and AWS best practices for security.

Rule query

edit

any where event.dataset == "aws.cloudtrail"
   and event.action == "PutBucketReplication"
   and event.outcome == "success"
   and stringContains(aws.cloudtrail.request_parameters, "Account")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Exfiltration
- ID: TA0010
- Reference URL: https://attack.mitre.org/tactics/TA0010/
Technique:
- Name: Transfer Data to Cloud Account
- ID: T1537
- Reference URL: https://attack.mitre.org/techniques/T1537/

« AWS S3 Bucket Server Access Logging Disabled AWS S3 Object Versioning Suspended »