name: AWS Lambda UpdateFunctionCode
id: 211b80d3-6340-4345-11ad-212bf3d0d111
version: 1
date: '2022-02-24'
author: Bhavin Patel, Splunk
status: production
type: Hunting
description: 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.
data_source: 
- AWS CloudTrail
search: '`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`'
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.
references:
- http://detectioninthe.cloud/execution/modify_lambda_function_code/
- https://sysdig.com/blog/exploit-mitigate-aws-lambdas-mitre/
tags:
  analytic_story:
  - Suspicious Cloud User Activities
  asset_type: AWS Account
  confidence: 90
  impact: 70
  message: User $user_arn$ is attempting to update the lambda function code of $function_updated$
    from this IP $src_ip$
  mitre_attack_id:
  - T1204
  observable:
  - name: src_ip
    type: IP Address
    role:
    - Attacker
  - name: user_arn
    type: User
    role:
    - Attacker
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - eventName
  - userAgent
  - errorCode
  risk_score: 63
  security_domain: cloud
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1204/aws_updatelambdafunctioncode/aws_cloudtrail_events.json
    sourcetype: aws:cloudtrail
    source: aws_cloudtrail
    update_timestamp: true