Maester

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Synopsis: Open-source PowerShell test automation framework for continuously monitoring Microsoft 365 / Entra ID security configuration.

Maester is built on top of Pester (the PowerShell test framework) and turns Microsoft security best practices into runnable tests, so configuration drift or a risky change can be caught automatically instead of relying on a one-off manual review. It ships with 140+ built-in tests, including the Entra ID Security Config Analyzer (EIDSCA) checks and Conditional Access checks, validated against Microsoft security baselines, MITRE ATT&CK, and CISA guidance. A run produces an HTML report with remediation guidance for anything that fails, and it integrates with GitHub Actions / Azure DevOps Pipelines to run on a schedule or on every tenant configuration change.

Unlike PingCastle, Maester is fully open source and free — there's no commercial licensing tier.

This repository additionally contains a complete set of custom CIS tests for Microsoft 365, on top of what Maester ships with out of the box.

Usage examples:

Install-Module Pester -Scope CurrentUser -SkipPublisherCheck -Force
Install-Module Maester -Scope CurrentUser
Install-MaesterTests

One-time setup: installs Pester and Maester, then downloads the ready-made Maester test suite into the current directory.

Connect-Maester
Invoke-Maester

Signs in to the tenant and runs all *.Tests.ps1 files found in the current directory and its subdirectories (including the CIS tests in this repository), producing an HTML report of the results.