This analytic is designed to detect IAM users attempting to update/modify AWS lambda code via the AWS CLI to gain persistence, futher access into your AWS environment and to facilitate planting backdoors. In this instance, an attacker may upload malicious code/binary to a lambda function which will be executed automatically when the funnction is triggered.
- Type: Hunting
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2022-02-24
- Author: Bhavin Patel, Splunk
- ID: 211b80d3-6340-4345-11ad-212bf3d0d111
Kill Chain Phase
- Actions on Objectives
- CIS 13
1 2 3 `cloudtrail` eventSource=lambda.amazonaws.com eventName=UpdateFunctionCode* errorCode = success user_type=IAMUser | stats count min(_time) as firstTime max(_time) as lastTime values(requestParameters.functionName) as function_updated by src_ip user_arn user_agent user_type eventName aws_account_id |`aws_lambda_updatefunctioncode_filter`
The SPL above uses the following Macros:
aws_lambda_updatefunctioncode_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
You must install Splunk AWS Add on and enable Cloudtrail logs in your AWS Environment.
Known False Positives
While this search has no known false positives, it is possible that an AWS admin or an autorized IAM user has updated the lambda fuction code legitimately.
Associated Analytic Story
|63.0||70||90||User $user_arn$ is attempting to update the lambda function code of $function_updated$ from this IP $src_ip$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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