20. The non-transitory computer-readable storage medium of claim 18 , further comprising: a client communication module for receiving from a client data identifying the web site and a file hosted by the web site.
18. A non-transitory computer-readable storage medium with executable computer program instructions embodied therein for providing security, the computer program instructions comprising: a hygiene cache module for receiving from a plurality of clients data describing client hygiene scores for the clients and describing a plurality of web sites visited by the clients, and for storing the client hygiene scores associated with the plurality of clients, the client hygiene score for a client calculated responsive to an amount of malicious software detected at the client based on a scan of the client; a hygiene computation module for calculating a secondary hygiene score for a web site of the plurality of web sites visited by the clients based at least in part on client hygiene scores of clients that visited the web site; and a reputation computation module for calculating and storing a reputation score for a file hosted by the web site responsive to the secondary hygiene score of the web site.