Attach A Malicious Lambda Layer (aws)

Platform	Author	Last Update
aws	Nick Jones	2024-12-02

An attacker may attach a Lambda layer to an existing function to override a library that is used by the function, and use that malicious code to execute AWS API calls with that functions function’s IAM role.

MITRE IDs

• T1525

Required Permissions

• lambda:UpdateFunctionConfiguration

Required Parameters

Name	Type	Description	Example Value
functionname	str	Name of the function to be targeted	example-function
layers	str	List of layers to add as space-separated ARNs	arn:aws:lambda:us-east-1:123456789012:layer:my-layer

Attacker Action

aws lambda update-function-configuration --function-name example-function --layers arn:aws:lambda:us-east-1:123456789012:layer:my-layer

Detection Case

ELK query

When logs are ingested into ELK, the following Lucene query can be used to identify relevant events.

eventName:UpdateFunctionConfiguration AND eventSource:lambda.amazonaws.com

Sigma Definition

---
title: Attach a Malicious Lambda Layer
id: 8fb105ea-19f8-4537-965a-cdc68200b8d9
status: experimental
author: Nick Jones
date: 2024-12-02
description: An attacker may attach a Lambda layer to an existing function to override a library that is used by the function, and use that malicious code to execute AWS API calls with that functions function's IAM role.
logsource:
  service: cloudtrail
detection:
  selection_source:
    - eventSource: "lambda.amazonaws.com"
  events:
    - eventName: "UpdateFunctionConfiguration"
  condition: selection_source and events
level: medium
tags:
  - attack.T1525

references:
  - https://docs.aws.amazon.com/lambda/latest/dg/API_UpdateFunctionConfiguration.html
  - https://docs.aws.amazon.com/cli/latest/reference/lambda/update-function-configuration.html
falsepositives:
  - Developers making legitimate changes to the environment. Verify whether the user identity, user agent, and/or hostname should be making changes in your environment.