1. A computer-implemented method of providing computer security, comprising: 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, the client hygiene score for a client calculated responsive to an amount of malicious software detected at the client; determining a secondary hygiene score for a web site of the plurality of web sites visited by the clients based at least in part on a number of clients with predominately good client hygiene scores and a number of clients with predominately bad client hygiene scores that visited the web site; identifying a file hosted by the web site; and calculating and storing a reputation score for the file responsive to the secondary hygiene score of the web site that hosts the file, the reputation score representing an assessment of whether the file is malicious.