There are several methods of verifying the alarm reported by a detection system; these include watchtowers, patrols, closed circuit television (CCTV), and slow scan CCTV. Physical devices used to delay an intruder may include barbed wire, electrified fencing, or moats and walls. Proper security system engineering minimizes the risk of system failure and matches the system to the risk assessment in order to provide the client with a cost- effective and reliable solution that meets both security and financial needs. The system must be able to neutralize the threat posed by any of the three principle categories of intruder, namely, the casual intruder, motivated but minimally trained intruder, and motivated and highly trained intruder.