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The following analytic identifies IAM users attempting to update or modify AWS Lambda code via the AWS CLI. It leverages CloudTrail logs to detect successful UpdateFunctionCode events initiated by IAM users. This activity is significant as it may indicate an attempt to gain persistence, further access, or plant backdoors within your AWS environment. If confirmed malicious, an attacker could upload and execute malicious code automatically when the Lambda function is triggered, potentially compromising the integrity and security of your AWS infrastructure.

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

  • Last Updated: 2024-05-13
  • Author: Bhavin Patel, Splunk
  • ID: 211b80d3-6340-4345-11ad-212bf3d0d111




ID Technique Tactic
T1204 User Execution Execution
Kill Chain Phase
  • Installation
  • DE.AE
  • CIS 10
`cloudtrail` 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 


The SPL above uses the following Macros:

:information_source: 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.

Required fields

List of fields required to use this analytic.

  • _time
  • eventName
  • userAgent
  • errorCode

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


Risk Score Impact Confidence Message
63.0 70 90 User $user_arn$ is attempting to update the lambda function code of $function_updated$ from this IP $src_ip$

: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.


Test Dataset

Replay any dataset to Splunk Enterprise by using our tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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