To surveil is to watch another, either by personal observation, technological means, or a combination of the two. Surveillance is an integral component for any security practice, but its object (the person surveilled), and the activities under scrutiny, are unknowing subjects. To have any effectiveness, surveillance needs to take place without notice or public awareness. The use of surveillance should be a blend of aggressive and cautious planning and tactics. Aggressive in the sense that it is one of the more remarkable tools in the security professional’s toolbox which should be used with regularity and cautiously employed because of the privacy implications of its usage.