DataSmith

Drupal builds in access rules to control who can and cannot access a site and in the Admin section of Drupal, you can see a nice list of the rules in place on the site, like below.

What it doesn't offer is a way to annote the rules to tell you why you added the rule. For instance, in six months it might be nice to have a note to tell me that the rule banning users from IP address 91.214.45.% was put in place because I was getting a ton of comment spam from there.

access rules table screenshot