Altor Networks, a 14-month-old start-up backed by $6 million in funding from Accel Partners and Foundation Capital, says the kind of security used on physical machines flat-out doesn't work in the virtual world and that you've got to think of virtualized machines as a network unto itself. Altor's thinking that way and claims to be able to make a virtual environment more secure than a physical one by putting the security at the network level, specifically on the virtual (software) switch.