[New Rule] Azure Compute Snapshot Deletion(s)

[terrancedejesus]

Fixes #5210

Pull Request

Issue link(s):

• [New Rule] Azure Compute Snapshot Deletion(s) #5210

Summary - What I changed

Adds detection coverage for unusual Azure Compute snapshot deletions. A threshold rule and a New Terms rule. Please see related issue for more details.

How To Test

Query can be used to test on data in TRADE stack.

Checklist

• Added a label for the type of pr: bug, enhancement, schema, maintenance, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Added the meta:rapid-merge label if planning to merge within 24 hours
• Secret and sensitive material has been managed correctly
• Automated testing was updated or added to match the most common scenarios
• Documentation and comments were added for features that require explanation

Contributor checklist

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?

[github-actions]

Rule: New - Guidelines

These guidelines serve as a reminder set of considerations when proposing a new rule.

Documentation and Context

• Detailed description of the rule.
• List any new fields required in ECS/data sources.
• Link related issues or PRs.
• Include references.

Rule Metadata Checks

• creation_date matches the date of creation PR initially merged.
• min_stack_version should support the widest stack versions.
• name and description should be descriptive and not include typos.
• query should be inclusive, not overly exclusive, considering performance for diverse environments. Non ecs fields should be added to non-ecs-schema.json if not available in an integration.
• min_stack_comments and min_stack_version should be included if the rule is only compatible starting from a specific stack version.
• index pattern should be neither too specific nor too vague, ensuring it accurately matches the relevant data stream (e.g., use logs-endpoint.process-* for process data).
• integration should align with the index. If the integration is newly introduced, ensure the manifest, schemas, and new_rule.yaml template are updated.
• setup should include the necessary steps to configure the integration.
• note should include any additional information (e.g. Triage and analysis investigation guides, timeline templates).
• tags should be relevant to the threat and align/added to the EXPECTED_RULE_TAGS in the definitions.py file.
• threat, techniques, and subtechniques should map to ATT&CK always if possible.

New BBR Rules

• building_block_type should be included if the rule is a building block and the rule should be located in the rules_building_block folder.
• bypass_bbr_timing should be included if adding custom lookback timing to the rule.

Testing and Validation

• Provide evidence of testing and detecting the expected threat.
• Check for existence of coverage to prevent duplication.

[imays11]

so is azure.resource.group something that is created for a group of snapshots in this case? I'm wondering why you need both fields here instead of just the azure.activitylogs.identity.claims_initiated_by_user.name field? Are you intending to capture the first time a user deletes any snapshot inside of a particular group of snapshots?

[terrancedejesus]

@imays11 Resource groups in Azure act as containers that organize and manage related resources for various operations. They’re typically at the root level of most activities. For instance, when creating a virtual network with associated instances, firewalls, and applications, all of these resources are usually placed within a single resource group.

We include the resource group in this context to ensure the alert only triggers when a user deletes snapshots in a resource group where they don’t typically perform such actions. This helps reduce noise and focus on anomalous behavior. False positives are expected for developers, engineers, or others who regularly manage and modify resources within their own groups.

It's very similar to some of the AWS tunings to be tenant focused, but at the next layer.

[imays11]

1. Is there ever an instance where azure.activitylogs.identity.claims_initiated_by_user.name field isn't populated?
2. Is azure.activitylogs.result_type: Accept or azure.activitylogs.result_signature: Accepted.Accepted equivalent to azure.activitylogs.properties.status_code: Accepted? If so should you use one of these in the query in place of the flattened field?

[terrancedejesus]

@imays11 - yes, there are instances where azure.activitylogs.identity.claims_initiated_by_user.name is not populated. Regarding the second question, there are several values I've seen in the telemetry here such as Accepted.Accepted or Accepted or Accepted.Created. result_type: Accept is consistent as a response from the API when the request occurs and is accepted.

[imays11]

same comment here about the use of a flattened field