From bdb357cbc283997cf80307a5a8503456e2a08576 Mon Sep 17 00:00:00 2001
From: patel-bhavin <bhavin.j.patel91@gmail.com>
Date: Mon, 28 Feb 2022 11:28:27 -0800
Subject: [PATCH] detection update

---
 .../cloud/aws_lambda_updatefunctioncode.yml   | 62 +++++++++++++++++++
 .../aws_lambda_updatefunctioncode.test.yml    | 13 ++++
 2 files changed, 75 insertions(+)
 create mode 100644 detections/cloud/aws_lambda_updatefunctioncode.yml
 create mode 100644 tests/cloud/aws_lambda_updatefunctioncode.test.yml

diff --git a/detections/cloud/aws_lambda_updatefunctioncode.yml b/detections/cloud/aws_lambda_updatefunctioncode.yml
new file mode 100644
index 0000000000..5e6e441585
--- /dev/null
+++ b/detections/cloud/aws_lambda_updatefunctioncode.yml
@@ -0,0 +1,62 @@
+name: AWS Lambda UpdateFunctionCode
+id: 211b80d3-6340-4345-11ad-212bf3d0d111
+version: 1
+date: '2022-02-24'
+author: Bhavin Patel, Splunk
+type: Hunting
+datamodel: []
+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. 
+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 Splunk App for AWS. This
+  search works with AWS CloudTrail logs.
+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 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
+  automated_detection_testing: passed
+  cis20:
+  - CIS 13
+  confidence: 90
+  context:
+  - Source:Cloud Data
+  - Scope:External
+  - Outcome:Allowed
+  - Stage:Execution
+  dataset:
+  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1204/aws_updatelambdafunctioncode/aws_cloudtrail_events.json
+  impact: 70
+  kill_chain_phases:
+  - Actions on Objectives
+  message: User $user_arn$ is attempting to create access keys for $requestParameters.userName$
+    from this IP $src$
+  mitre_attack_id:
+  - T1204
+  nist:
+  - PR.DS
+  - PR.AC
+  - DE.CM
+  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
diff --git a/tests/cloud/aws_lambda_updatefunctioncode.test.yml b/tests/cloud/aws_lambda_updatefunctioncode.test.yml
new file mode 100644
index 0000000000..9a2b157e71
--- /dev/null
+++ b/tests/cloud/aws_lambda_updatefunctioncode.test.yml
@@ -0,0 +1,13 @@
+name: AWS Lambda UpdateFunctionCode Unit Test
+tests:
+- name: AWS Lambda UpdateFunctionCode
+  file: cloud/aws_lambda_updatefunctioncode.yml
+  pass_condition: '| stats count | where count > 0'
+  earliest_time: '-7d'
+  latest_time: 'now'
+  attack_data:
+  - file_name: aws_cloudtrail_events.json
+    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