There are many ways to monitor Active Directory activities in an infastrcure. Some tools are just to monitor the AD services and some tools are to monitor services as well as the activities. Service level monitoring is the easy part and any monitoring tool with windows service monitoring can monitor the status of the AD services. Tools likes SCOM allows to monitor services in more granular level.
More than any other system active directory in an organization important in security perspective. Even a small change in Organization’s AD can cause a major business impact. Preventing any unauthorized access, unplanned change in AD environment should prevent in first place but if similar thing happened in your AD environment you should have enough information to answer questions such as…