Some clever scientists have reviewed current events to try and find a universal pattern to terrorism and published a paper with their results:

We report a remarkable universality in the patterns of violence arising in three high-profile ongoing wars, and in global terrorism. Our results suggest that these quite different conflict arenas currently feature a common type of enemy, i.e. the various insurgent forces are beginning to operate in a similar way regardless of their underlying ideologies, motivations and the terrain in which they operate. We provide a microscopic theory to explain our main observations. This theory treats the insurgent force as a generic, self-organizing system which is dynamically evolving through the continual coalescence and fragmentation of its constituent groups.

It looks like they were trying to prove the old adage that ideologies, motives and terrain do not impact methods used by insurgent forces. I think that would be useful as an elimination of factors that are often mistakenly assumed to influence method, rather than proof of universality. In other words, does the universality of a hammer as a tool for hammering surprise anyone? Does it matter if the people who use hammers for hammering spend their money on different causes?