Reading on Active Directory

AD and Disaster Recovery
https://www.reddit.com/r/sysadmin/wiki/ms/activedirectorydisasterrecovery

What does DCDIAG do…?
https://docs.microsoft.com/en-us/archive/blogs/askds/what-does-dcdiag-actually-do

How Active Directory Authentication Works?
http://www.rebeladmin.com/2018/06/active-directory-authentication-works/

AD DS security is key for any environment as it is foundation of identity protection. Before look in to improvements of AD DS security in an environment, it is important to understand how Active Directory authentication works with Kerberos. In this post I am going to explain how AD authentication works behind the scene.