MOSS Search Rules deal with the actual quantity of SharePoint crawls – excessive values of these properties may degrade the performance of your SharePoint environment.

These Rules are also broken down into the following types:

Deep Crawl Rules

These Rules check if the percentage of deep crawls per site exceed a certain threshold.

Excessive Crawl Rules

These Rules check if the number of crawls per SSP exceed a certain threshold. SSP stands for Shared Service Providers. SSPs allow SharePoint administrators to centrally manage and share certain services between various sites – such as profile information obtained from an Active Directory.