A side note: the recent rise in terrorism is closely tied to the attention it creates. Their purpose is to change the situation (locally or globally), and for that they need to be heard. We live in an unprecedented situation, where killing few people can make your voice heard globally, and your opinion to be weighted by billions of people.
I think this phenomenon is what gives rise to the modern form of terrorism against random civilians, which as far as I know didn't happen before. Until late 20th century terrorism always targeted specific targets: politicians, rulers, opponents, because attacking random people was not effective.