Microsoft 365 Teams Guest Access Enabled

Identifies when guest access is enabled in Microsoft Teams. Guest access in Teams allows people outside the organization to access teams and channels. An adversary may enable guest access to maintain persistence in an environment.

Rule type: query

Rule indices:

filebeat-*
logs-o365*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-30m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://docs.microsoft.com/en-us/powershell/module/skype/get-csteamsclientconfiguration?view=skype-ps

Tags:

Elastic
Cloud
Microsoft 365
Continuous Monitoring
SecOps
Configuration Audit

Version: 8

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Setup

The Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.

Rule query

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event.dataset:o365.audit and event.provider:(SkypeForBusiness or MicrosoftTeams) and
event.category:web and event.action:"Set-CsTeamsClientConfiguration" and
o365.audit.Parameters.AllowGuestUser:True and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Account Manipulation
- ID: T1098
- Reference URL: https://attack.mitre.org/techniques/T1098/

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