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Export Custom Rules

This guide covers how to export custom rules that are already deployed on Sentinel and how to test them.

Export rules from Sentinel to JSON

If you have yet to create a custom rule, please refer to the following guide by Microsoft. Create custom analytics rules to detect threats. Once done, follow the steps described below.

  1. Navigate to your Sentinel workspace
  2. Click on Analytics
  3. Check the checkbox for the custom rule you wish to export
  4. Click on “Export” button at the top


Convert rules from JSON to yaml

To convert the rules from JSON to yaml manually. Please refer to the example below for the format and fill in accordingly.


Text format to copy paste

  id: 71736563-3347-3634-5747-5638374a4253
    createIncident: true
      enabled: false
      groupByAlertDetails: []
      groupByCustomDetails: []
      groupByEntities: []
      lookbackDuration: PT5H
      matchingMethod: AllEntities
      reopenClosedIncident: false
  displayName: 'DNS events related to mining pools'
  description: |
    Identifies IP addresses that may be performing DNS lookups associated with common currency mining pools.
  severity: Low
  enabled: true
  query: |
    | where Name contains "."
    | where Name has_any ("", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "", "",
    "", "", "", "", "", "", "", "",
    "", "", "", "", "")
    | extend timestamp = TimeGenerated, IPCustomEntity = ClientIP, HostCustomEntity = Computer
  queryFrequency: 1D
  queryPeriod: 1D
  triggerOperator: GreaterThan
  triggerThreshold: 0
  suppressionDuration: PT5H
  suppressionEnabled: false
    - entityType: Host
        - identifier: FullName
          columnName: HostCustomEntity
    - entityType: IP
        - identifier: Address
          columnName: IPCustomEntity
  tactics: ['Impact']
  techniques: ['T1496']
  kind: Scheduled


Please take special note on the entity mapping and refer to this document to understand better and the best practices

Test custom yaml rules

Once you have converted the rules, you can now perform testing to check if they will be deployed correctly.

Set up testing environment

  1. Clone infrastructure-live repository
  2. Change directory to azure/dev/southeastasia/<prefix>-log-analytics/services/
  3. Create a new folder under the above directory. e.g sentinel-rules-testing
  4. Copy config.hcl and terragrunt.hcl from the sentinel-rules folder
  5. Create a new directory within the current folder content/rules
  6. In the newly copied config.hcl remove the comment from # content_path_rules = "content/rules"

The final folder structure should look like this


Add custom rules into testing environment

  1. Move/copy all custom yaml rules into the content/rules folder you have just created
  2. Open config.hcl and under the additional_rules field add in each of the custom rules

It should be look similar to this


Please note that if you have specified a different content_path_rules you will have to follow that instead.

Logg into Azure and setting subscription

  1. In your terminal, run az login and select the appropriate account
  2. Once signed in, run az account set --subscription <SUBSCRIPTION_ID> to set your subscription.

Run test

  1. In your terminal, change directory to sentinel-rules-testing
  2. Run terragrunt plan
  3. Fix any errors that is reported and run the above command again
  4. Once fixed, run terragrunt apply
  5. If the results looks desirable, enter yes when prompted
  6. Open up Sentinel and check if your custom rules have successfully deployed

Clean up

Once your testing is complete, clean up the Sentinel by running terragrunt destroy to delete the newly created custom rules on Sentinel

If you wish to deploy these on customer environment please refer correct guide below.

Potential Errors and Solutions

This section covers some of the potential errors that you may face and how to resolve them.

Backend initialization required, please run “terraform init


Please check if you are logged into the correct Azure account with the correct subscription set.

If the error still persist, run az logout and sign in by following Logging into Azure and setting subscription

Module source has changed

module-source-has-changed Run the following command

terragrunt init

Debug Terragrunt

If the error you are facing is not one of the above, you can execute the following command to enable debugging. terragrunt plan --terragrunt-log-level debug --terragrunt-debug

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