The threat of terrorism consists of a number of unknowns to be dealt with.
- Firstly, the explosive devices used in terrorist attacks. These range from small, person-borne containers, rucksacks and suitcases to larger, vehicle-borne devices.
- Secondly, the methods and tools used by the terrorists. These are related to the nature, capacity and tactics of the attackers.
- And thirdly, the on-site security measures. To a high extent, they determine the success and severity of a potential attack – for instance by enforcing a stand-off distance and physically excluding certain charge sizes.
The definition of a sound security system is one which reduces the risk of large explosive devices coming close to critical assets.