A system and method of conserving network bandwidth by controlling access to resources. A filtering service determines if a resource should be blocked or allowed to pass between computers on the network based on information about the resource including the path and any query parameters in the URI along with any available metadata about the resource. The metadata may be retrieved from the remote hose, generated based on the content of the resource, or any combination thereof. One or more filtering algorithms may be engaged to compare the information about the resource to filtering rules to determine whether access to the resource is allowed. The information about the resource, and the result of the filtering algorithm may be stored to reduce the time required to make future determinations for the same resource, or for similar resources.