IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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Suspicious Microsoft 365 Mail Access by ClientAppId

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Suspicious Microsoft 365 Mail Access by ClientAppId

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Identifies when a Microsoft 365 Mailbox is accessed by a ClientAppId that was observed for the fist time during the last 10 days.

Rule type: new_terms

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://www.cisa.gov/news-events/cybersecurity-advisories/aa23-193a

Tags:

Domain: Cloud
Data Source: Microsoft 365
Use Case: Configuration Audit
Tactic: Initial Access

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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Rule query

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event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:MailItemsAccessed and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Initial Access
- ID: TA0001
- Reference URL: https://attack.mitre.org/tactics/TA0001/
Technique:
- Name: Valid Accounts
- ID: T1078
- Reference URL: https://attack.mitre.org/techniques/T1078/

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