1. A system for protecting computers against cache poisoning, the system comprising: one or more processors; a memory accessible by at least one of the processors; a cache-entity table configured to maintain a plurality of associations between a plurality of data caches and a plurality of entities, wherein each of said data caches is associated with a different one of said entities; and a cache manager configured to receive data that is associated with any of said entities and store said received data in any of said data caches that said cache-entity table indicates is associated with said entity; receive a data request from any of said entities and retrieve said requested data from any of said data caches that said cache-entity table indicates is associated with said requesting entity; identify any entry that appears in at least a predefined number of said data caches, and move said identified entry from said data caches to a global cache, said global cache separate from said data caches, wherein subsequent data requests for said identified entry are satisfied by retrieving said identified entry directly from said global cache; and wherein any of said cache-entity table and cache manager are implemented in either of computer hardware and computer software embodied in a computer-readable medium.