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Description

The search looks for AWS CloudTrail events to detect if any network ACLs were created with all the ports open to a specified CIDR.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2021-01-11
  • Author: Bhavin Patel, Patrick Bareiss, Splunk
  • ID: ada0f478-84a8-4641-a3f1-d82362d6bd75

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1562.007 Disable or Modify Cloud Firewall Defense Evasion
T1562 Impair Defenses Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 13
CVE 


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`cloudtrail` eventName=CreateNetworkAclEntry OR eventName=ReplaceNetworkAclEntry requestParameters.ruleAction=allow requestParameters.egress=false requestParameters.aclProtocol=-1 
| append [search `cloudtrail` eventName=CreateNetworkAclEntry OR eventName=ReplaceNetworkAclEntry requestParameters.ruleAction=allow requestParameters.egress=false requestParameters.aclProtocol!=-1 
| eval port_range='requestParameters.portRange.to' - 'requestParameters.portRange.from' 
| where port_range>1024] 
| fillnull 
| stats count min(_time) as firstTime max(_time) as lastTime by userName user_arn userIdentity.principalId eventName requestParameters.ruleAction requestParameters.egress requestParameters.aclProtocol requestParameters.portRange.to requestParameters.portRange.from src userAgent requestParameters.cidrBlock 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` 
| `aws_network_access_control_list_created_with_all_open_ports_filter`

Macros

The SPL above uses the following Macros:

:information_source: aws_network_access_control_list_created_with_all_open_ports_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • eventName
  • requestParameters.ruleAction
  • requestParameters.egress
  • requestParameters.aclProtocol
  • requestParameters.portRange.to
  • requestParameters.portRange.from
  • requestParameters.cidrBlock
  • userName
  • userIdentity.principalId
  • userAgent

How To Implement

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, and configure your AWS CloudTrail inputs.

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

RBA

Risk Score Impact Confidence Message
48.0 60 80 User $user_arn$ has created network ACLs with all the ports open to a specified CIDR $requestParameters.cidrBlock$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 2