Techniques for network security are disclosed. In some implementations, an evaluation module determines whether a network communication from a source computing system to a destination computing system is allowable. The allowability of the communication is determined based properties of the network communication, such as a source or destination address, a port number, a time of day, a geographic location, and the like. If the communication is disallowed, the evaluation module or a related component redirects the communication to an alternative computing system that masquerades as the destination communication system.