Active Directory

Microsoft's directory service that stores user accounts, computers and permissions for a Windows network and controls who can sign in and what they can reach.

Active Directory (often shortened to AD) is the central phone book and gatekeeper for many Windows-based offices. It holds user names, passwords, group memberships and computer accounts, and it applies security settings across the network. Many businesses now use Microsoft Entra ID, the cloud-based identity service formerly known as Azure Active Directory, either alongside or instead of an on-premises server.

Because Active Directory controls access to almost everything, it is a prime target for attackers. Once someone gains administrator rights in AD, they can often reach every computer and file in the organization. Old accounts belonging to former staff, weak service account passwords and too many administrators are common weaknesses in small business environments.

Practical tip: ask your IT provider for a simple report of all enabled accounts and all members of administrator groups. Disable anything you do not recognize or no longer need, and make sure administrator accounts are protected with multi-factor authentication.