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Description

The following analytic identifies users with KMS keys performing encryption operations on S3 buckets. It leverages AWS CloudTrail logs to detect the CopyObject event where server-side encryption with AWS KMS is specified. This activity is significant as it may indicate unauthorized or suspicious encryption of data, potentially masking exfiltration or tampering efforts. If confirmed malicious, an attacker could be encrypting sensitive data to evade detection or preparing it for exfiltration, posing a significant risk to data integrity and confidentiality.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-18
  • Author: Rod Soto, Patrick Bareiss Splunk
  • ID: 884a5f59-eec7-4f4a-948b-dbde18225fdc

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1486 Data Encrypted for Impact Impact
Kill Chain Phase
  • Actions On Objectives
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`cloudtrail` eventName=CopyObject requestParameters.x-amz-server-side-encryption="aws:kms" 
| rename requestParameters.bucketName AS bucketName, requestParameters.x-amz-copy-source AS src_file, requestParameters.key AS dest_file 
| stats count min(_time) as firstTime max(_time) as lastTime values(bucketName) as bucketName values(src_file) AS src_file values(dest_file) AS dest_file values(userAgent) AS userAgent values(region) AS region values(src) AS src by user 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` 
|`aws_detect_users_with_kms_keys_performing_encryption_s3_filter`

Macros

The SPL above uses the following Macros:

:information_source: aws_detect_users_with_kms_keys_performing_encryption_s3_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • eventName
  • requestParameters.x-amz-server-side-encryption
  • requestParameters.bucketName
  • requestParameters.x-amz-copy-source
  • requestParameters.key
  • userAgent
  • region

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

There maybe buckets provisioned with S3 encryption

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
15.0 30 50 User $user$ with KMS keys is performing encryption, against S3 buckets on these files $dest_file$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 3