Detection: ASL AWS Network Access Control List Created with All Open Ports

Updated Date: 2025-01-09 ID: a2625034-c2de-44fc-b45c-7bac9c4a7974 Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of AWS Network Access Control Lists (ACLs) with all ports open to a specified CIDR. It leverages AWS CloudTrail events, specifically monitoring for CreateNetworkAclEntry or ReplaceNetworkAclEntry actions with rules allowing all traffic. This activity is significant because it can expose the network to unauthorized access, increasing the risk of data breaches and other malicious activities. If confirmed malicious, an attacker could exploit this misconfiguration to gain unrestricted access to the network, potentially leading to data exfiltration, service disruption, or further compromise of the AWS environment.

 1`amazon_security_lake` api.operation=CreateNetworkAclEntry OR api.operation=ReplaceNetworkAclEntry status=Success 
 2| spath input=api.request.data path=ruleAction output=ruleAction 
 3| spath input=api.request.data path=egress output=egress 
 4| spath input=api.request.data path=aclProtocol output=aclProtocol 
 5| spath input=api.request.data path=cidrBlock output=cidrBlock 
 6| spath input=api.request.data path=networkAclId output=networkAclId 
 7| search ruleAction=allow AND egress=false AND aclProtocol=-1 AND cidrBlock=0.0.0.0/0 
 8| fillnull 
 9| stats count min(_time) as firstTime max(_time) as lastTime by api.operation actor.user.uid actor.user.account.uid http_request.user_agent src_endpoint.ip cloud.region networkAclId cidrBlock 
10| rename actor.user.uid as user, src_endpoint.ip as src_ip, cloud.region as region, http_request.user_agent as user_agent, actor.user.account.uid as aws_account_id 
11| `security_content_ctime(firstTime)`
12| `security_content_ctime(lastTime)` 
13| `asl_aws_network_access_control_list_created_with_all_open_ports_filter`

Data Source

Name Platform Sourcetype Source
ASL AWS CloudTrail AWS icon AWS 'aws:asl' 'aws_asl'

Macros Used

Name Value
amazon_security_lake sourcetype=aws:asl
asl_aws_network_access_control_list_created_with_all_open_ports_filter search *
asl_aws_network_access_control_list_created_with_all_open_ports_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1562.007 Disable or Modify Cloud Firewall Defense Evasion
T1562 Impair Defenses Defense Evasion
Exploitation
DE.CM
CIS 13
Magic Hound

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

The detection is based on Amazon Security Lake events from Amazon Web Services (AWS), which is a centralized data lake that provides security-related data from AWS services. To use this detection, you must ingest CloudTrail logs from Amazon Security Lake into Splunk. To run this search, ensure that you ingest events using the latest version of Splunk Add-on for Amazon Web Services (https://splunkbase.splunk.com/app/1876) or the Federated Analytics App.

Known False Positives

It's possible that an admin has created this ACL with all ports open for some legitimate purpose however, this should be scoped and not allowed in production environment.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

User $user$ has created network ACLs with all the ports opens to $cidrBlock$

Risk Object Risk Object Type Risk Score Threat Objects
user user 48 src_ip

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_asl aws:asl
Integration ✅ Passing Dataset aws_asl aws:asl

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: 1