DFIR-O365RC: PowerShell module for Office 365 and Azure AD log collection

by do son · March 25, 2021

DFIR-O365RC

The DFIR-O365RC PowerShell module is a set of functions that allow the DFIR analyst to collect logs relevant for Office 365 Business Email Compromise investigations.

The logs are generated in JSON format and retrieved from two main data sources:

Office 365 Unified Audit Logs.
Azure AD sign-ins logs and audit logs.

The two data sources can be queried from different endpoints:

Data source / Endpoint	History	Performance	Scope	Pre-requisites (OS or Azure)
Unified Audit Logs / Exchange Online PowerShell	90 days	Poor	All Office 365 logs (Azure AD included)	None
Unified Audit Logs / Office 365 Management API	7 days	Good	All Office 365 logs (Azure AD included)	Azure App registration
Azure AD Logs / Azure AD PowerShell Preview	30 days	Good	Azure AD sign-ins and audit events only	Windows OS only
Azure AD Logs / MS Graph API	30 days	Good	Azure AD sign-ins and audit events only	None

DFIR-O365RC is a forensic tool, its aim is not to monitor in real-time your Office 365 infrastructure: Please use the Office 365 Management API if you want to analyze data in real-time with a SIEM.

DFIR-O365RC will fetch data from:

Azure AD Logs using the MS Graph API because performance is good, history is 30 days and it works on PowerShell Core.
Unified Audit Logs using Exchange online PowerShell despite poor performance, history is 90 days and it works on PowerShell Core.

As a result, DFIR-O365RC works also on Linux or Mac, as long as you have PowerShell Core and a browser in order to use device login.

Functions included in the module

The module has 6 functions:

Function name	Data Source/History	Performance	Completeness	Details
Get-O365Full	Unified audit logs/90 days	Poor	All unified audit logs	A subset of logs per record type can be retrieved. Use only on a small tenant or a short period of time
Get-O365Light	Unified audit logs/90 days	Good	A subset of unified audit logs only	Only a subset of operations considered of interest is retrieved.
Get-DefenderforO365	Unified audit logs/90 days	Good	A subset of unified audit logs only	Retrieves Defender for Office 365 related logs. Requires at least an E5 license or a license plan such as Microsoft Defender for Office 365 Plan or cloud app security
Get-AADLogs	Azure AD Logs/30 days	Good	All Azure AD logs	Get tenant general information, all Azure sign-ins and audit logs. Azure AD sign-ins logs have more information than Azure AD logs retrieved via Unified audit logs.
Get-AADApps	Azure AD Logs/30 days	Good	A subset of Azure AD logs only	Get Azure audit logs related to Azure applications and service principals only. The logs are enriched with application or service principal object information.
Search-O365	Unified audit logs/90 days	Depends on the query	A subset of unified audit logs only	Search for activity related to a particular user, IP address or use the freetext query.

When querying Unified audit logs you are limited to 3 concurrent Exchange Online Powershell sessions. DFIR-O365RC will try to use all available sessions, please close any existing session before launching the log collection.