How it all worked was that they had purchased and installed some kind of high-tech system that used cameras and machine vision to notice human-shaped objects moving around on the property, and then attempted to perform "IFF" on them. Rufus knew from the military that this meant "Identification Friend or Foe." If the imagery was good enough, facial recognition would do the trick, but lots of times it wasn’t, and in any case people frequently wore earthsuits that got in the way of the optical path. So everyone was encouraged to wear a little device called an "iffy," which seemed to be a cross between an ID badge and the kind of transponder typically installed on aircraft so that air traffic controllers could tell one blip from another. The iffy, which was about the size of a phone, was apparently complicated and expensive. So you could get along without one if you were just working inside a building that had the usual security barrier at the entrance. But anyone roaming around the property at large needed to have an iffy that was up and running. When the high-tech system noticed a free-ranging humanoid life-form on the property who was not so equipped, drones would head that way with Black Hats in hot pursuit. Naturally all the net runners, sail chasers, et cetera had iffies as a matter of course.