Monitoring site access via an intervening control layer within a client is disclosed. In one embodiment of the invention, a computerized system includes a plurality of sites, a monitoring server, and a client. Each site has content referenced be addresses. The monitoring server maintains a database of permissible content on at least one of the plurality of sites, where the permissible content is also referenced by addresses. The client has an intervening control layer within an otherwise standard mechanism by which programs running on the client access the content on the plurality of sites. The intervening control layer polls the monitoring server to determine whether a program attempting to access content on one of the sites as referenced by an address should be permitted to do so.