ID | Technique | Tactic |
---|---|---|
T1562.007 | Disable or Modify Cloud Firewall | Defense Evasion |
T1562 | Impair Defenses | Defense Evasion |
Detection: AWS Network Access Control List Deleted
Description
The following analytic detects the deletion of AWS Network Access Control Lists (ACLs). It leverages AWS CloudTrail logs to identify events where a user deletes a network ACL entry. This activity is significant because deleting a network ACL can remove critical access restrictions, potentially allowing unauthorized access to cloud instances. If confirmed malicious, this action could enable attackers to bypass network security controls, leading to unauthorized access, data exfiltration, or further compromise of the cloud environment.
Search
1`cloudtrail` eventName=DeleteNetworkAclEntry requestParameters.egress=false
2| fillnull
3| stats count min(_time) as firstTime max(_time) as lastTime by user_arn userIdentity.principalId eventName requestParameters.egress src userAgent
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| `aws_network_access_control_list_deleted_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
AWS CloudTrail DeleteNetworkAclEntry | AWS | 'aws:cloudtrail' |
'aws_cloudtrail' |
N/A |
Macros Used
Name | Value |
---|---|
cloudtrail | sourcetype=aws:cloudtrail |
aws_network_access_control_list_deleted_filter | search * |
aws_network_access_control_list_deleted_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Risk Event | True |
Implementation
You must install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your AWS CloudTrail inputs.
Known False Positives
It's possible that a user has legitimately deleted a network ACL.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
User $user_arn$ from $src$ has sucessfully deleted network ACLs entry (eventName= $eventName$), such that the instance is accessible from anywhere | 5 | 10 | 50 |
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | aws_cloudtrail |
aws:cloudtrail |
Integration | ✅ Passing | Dataset | aws_cloudtrail |
aws:cloudtrail |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 3