2026年9月17日

このエピソードについて

Active Directory Security Testing in Maester 2.2

Active Directory is not dead. It is nearly thirty years old, Microsoft is still shipping new capabilities and new telemetry for it, and most of the forests running today will outlive the people currently administering them. What has changed is that you can now test it the same way you test your cloud tenant.

Maester, the open-source PowerShell testing framework, added Active Directory coverage: 269 opt-in checks across 19 areas, from users, groups, computers and service principal names through GPO state, DACLs, DNS, trusts, replication and schema. They run against your domain, not your tenant, and they are off unless you explicitly connect to Active Directory.

Mike Soule, who wrote and validated that test suite, and Sam Erde, Microsoft MVP and author of DLLPickle, join Merill at HIP Conf in Nashville to go through what the tests cover, how to run them safely, and where the project is heading.

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Operational health is not the same as a security finding

The design decision that makes these tests usable is the split between operational patterns and security controls. Six groups nested in a row is not a vulnerability. Nesting is an intentional, functional capability. It is also nearly impossible to reason about when you are trying to work out where a permission actually comes from, and that is how incidents happen.

So not every test is pass/fail. Some exist to be investigated and monitored, and Maester’s tagging lets you baseline them and watch whether an anti-pattern is spreading or receding over time. The underlying guidance is a blend: years of health checks across dozens of forests, community research from teams like Semperis and SpecterOps, and Microsoft’s own documentation — which, for a product people keep declaring dead, is currently some of the best documentation and logging Microsoft ships. The new NTLM auditing in Windows Server is the example: the who, the why and the where of every NTLM authentication, instead of replaying events and correlating them yourself.

Maester is not trying to replace the likes of PingCastle, Purple Knight or Locksmith. Those tools offer real value, and the conversation now is about bringing those perspectives into one central platform.

The permissions you actually need

Everything the AD tests do is read-only. A plain domain user gets a surprising amount, because a directory is built to be readable — you will simply get a subset of the tests. The full set needs tier-zero read access, because some tests reach objects in the configuration container. In a tiered environment, that means running as a tier-zero admin from a privileged admin workstation.

Interactively, there is nothing to set up beyond line of sight to a domain controller, the ActiveDirectory module and PowerShell. The AD tests are excluded by default and have to be requested by tag. For automation, run a local runner, or give a container runtime a path back to a domain controller. Today the tests run as the logged-in user’s domain credentials; alternate credentials and group managed service accounts are on the road map.

Tiering, ESAE and the enterprise access model

There are no explicit tiering tests yet, but they are coming now that Microsoft has published implementation guidance. The history is worth knowing. ESAE — the Enhanced Security Admin Environment, the red forest — solved a real problem: inside Active Directory, a domain admin is trusted implicitly, so the source of authority needs to sit somewhere that is not self-referential. A separate management forest achieves that, at a cost in operational complexity that most organisations could not sustain. Microsoft has since moved to the enterprise access model, and in practice most teams landed in the middle: tiering based on access control, with tier zero for core identity infrastructure, tier one for servers, databases and applications, and tier two for workstations and the workforce.

The advice is not all-or-nothing. Any amount of effort you put into tiering is a good investment. Where Maester helps is codifying Microsoft’s recommended implementation as tests you can actually check yourself against, including the DACL and inheritance anti-patterns that accumulate through ordinary operations.

What is coming next

The dependency on the ActiveDirectory PowerShell module is on its way out. Almost all of this work is LDAP-level, so a .NET-based approach covers the vast majority of tests with no module dependency — which opens up Linux, macOS and non-domain-joined machines. Multi-domain aggregation is in progress; today a run covers a single domain at a time. And Maester 3 is being planned around a new engine for the built-in tests, with multi-threading and parallel execution, licensing handled centrally instead of inside every test, and Pester retained for backward compatibility and custom tests.

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About Michael Soule

Mike Soule is a Maester co-maintainer and National Director of Enterprise Architecture at Sentinel Technologies, where he works with enterprise customers on identity, cloud and security. He wrote and validated the Active Directory test suite that shipped in Maester 2.2 — 269 opt-in checks across 19 areas — and has been the project’s leading test contributor since the night after Maester’s launch talk at the PowerShell Conference, when he turned up the next morning with roughly thirty CISA tests already written.

LinkedIn - https://www.linkedin.com/in/mikesoule/

GitHub - https://github.com/soulemike

About Sam Erde

Sam Erde is a Maester co-maintainer and a Microsoft MVP, working at Patriot Consulting. He has spent more than twenty years in PowerShell, Active Directory, Group Policy, Exchange and Microsoft 365, contributes to open-source defensive tooling including Locksmith, and wrote DLLPickle, the module that gets you out of assembly version conflicts when several Microsoft modules are loaded in one session.

LinkedIn - https://www.linkedin.com/in/samerde/

GitHub - https://github.com/SamErde