They don't, at least not very well. Hiro runs between two of the security daemons and heads for the wall of the cube. He finally gets there, slamming into it, coming to a dead stop. The security daemons have all turned around and are chasing him. They can figure out where he is—the computer tells them that much—but they can't do much to him. Like the bouncer daemons in The Black Sun, which Hiro helped write, they shove people around by applying basic rules of avatar physics. When Hiro is invisible, there is very little for them to shove. But if they are well written, they may have more subtle ways of messing him up, so he's not wasting any time. He pokes his katana through the side of the cube and follows it through the wall and out the other side.