Identifying which infrastructures are critical

The terrorist attacks of September 11, 2001 in the US and the attacks in Madrid on March 11, 2004 have demonstrated that our society is very vulnerable. Heuristics is one approach to analyze which infrastructures are critical and vulnerable. However, this may not be the best approach. Indeed, classical terrorist methods involve the use of explosive or highly flammable material. The use of bacteriological, toxic or nuclear dirty bomb is now often mentioned. However, the attacks on September 11 relied on a technique not used before and not studied extensively. We will discuss several methods that can be used to analyze this topic more scientifically. The methods are independent of the type of attacks the enemy uses, whether, e.g. a traditional bomb or cyber terrorism. We survey methods that use tools from artificial intelligence, data mining, economic models, and reliability.