A security system provides a defense from known and unknown viruses, worms, spyware, hackers, and social engineering attacks. The system can implement centralized policies that allow an administrator to approve, block, quarantine, or log file activities. The system can provide and update a security value that causes host computers to change security levels for a number of different policies. The policies are grouped into a master set of policies and options which are propagated to the hosts from a centralized server. The security value is stored on the hosts and the server, and changes of the value on the server are propagated to the hosts.