Sure... But i think an organisation like anonymous would be strong enough to hit them where it hurts: their social media campaign... They can encrypt most things, but not their twitter and facebook. It would be meaningless if they posted encrypted messages on facebook, because it would be useless as a tool to attract easily brainwashed kids.
Unfortunately most brainwashed "kids" they attract via their priests in various big cities over the world.
But I hope that Anonymous can find out something more, like their servers, if any.
Guerrillas are hard to fight, but I am sure they have some central points of command. If those are revealed and hacked, a lot o interesting info will flood out.
It will be very hard to harm ISIS in that way. Almost every intelligence agency is trying that for a while with very limited success cause ISIS use very unconventional methods to communicate and coordinate. Still, it is good to see that ppl is getting enough if those barbarians and try to do what they can. It will be fun to watch what those enthusiasts can do. In my opinion, Europe should play very hard on this ball at home and at middle east.