In the security world, there is a truism that defense is harder than offense because it's an asymmetric playing field. The bad guys need only find one path into an environment -- one place where everything hasn't been done perfectly -- while those charged with securing that environment need to protect against intrusions everywhere. The asymmetry is apparent in other respects as well. For example, a large percentage of a company's staff members may go home at night, but attackers can operate from wherever, whenever.