Azure External Guest User Invitation

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Identifies an invitation to an external user in Azure Active Directory (AD). Azure AD is extended to include collaboration, allowing you to invite people from outside your organization to be guest users in your cloud account. Unless there is a business need to provision guest access, it is best practice avoid creating guest users. Guest users could potentially be overlooked indefinitely leading to a potential vulnerability.

Rule type: query

Rule indices:

  • filebeat-*
  • logs-azure*

Severity: low

Risk score: 21

Runs every: 5 minutes

Searches indices from: now-25m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Cloud
  • Azure
  • Continuous Monitoring
  • SecOps
  • Identity and Access

Version: 101 (version history)

Added (Elastic Stack release): 7.10.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Guest user invitations may be sent out by a system or network administrator. Verify whether the username, hostname, and/or resource name should be making changes in your environment. Guest user invitations from unfamiliar users or hosts should be investigated. If known behavior is causing false positives, it can be exempted from the rule.

Investigation guide

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Rule query

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event.dataset:azure.auditlogs and
azure.auditlogs.operation_name:"Invite external user" and
azure.auditlogs.properties.target_resources.*.display_name:guest and
event.outcome:(Success or success)

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 101 (8.6.0 release)
  • Formatting only
Version 100 (8.5.0 release)
  • Formatting only
Version 7 (8.4.0 release)
  • Formatting only
Version 5 (7.13.0 release)
  • Formatting only
Version 4 (7.12.0 release)
  • Formatting only
Version 3 (7.11.2 release)
  • Formatting only
Version 2 (7.11.0 release)
  • Updated query, changed from:

    event.dataset:azure.auditlogs and
    azure.auditlogs.operation_name:"Invite external user" and
    azure.auditlogs.properties.target_resources.*.display_name:guest and
    event.outcome:Success