1. A method for a particular device to apply a flexible security policy that is automatically adjusted over time as required for connection to different networks, the method comprising: (a) receiving a request from the particular device for a connection to a particular network, said particular device applying an initial security policy selected from a plurality of security policies available for governing connections, each security policy governing connections with a specific set of constraints; (b) based on said particular network and said plurality of security policies available to said particular device, determining a current merged policy to apply to said particular device for governing said connection to said particular network, by merging said initial security policy with at least one other of the security policies available for governing connections; (c) allowing said connection to said particular network to proceed with said current merged policy applied to said particular device; and (d) repeating steps (a)-(c) for a plurality of connections to different networks, thereby automatically adjusting the security policy applied to the particular device based on the particular device's current connections.