cyber war between non-state actors 

From Islamic State: The Digital Caliphate, pg 16:

To date, the most effective cyber- retaliation on Islamic State for the murderous January 2015 Paris attacks (on satirical magazine Charlie Hebdo and a kosher supermarket) has come from an unlikely source – the veteran anarchist hacking collective Anonymous. Anonymous declared war on IS in January 2015 by means of a dramatic video and swiftly followed with the destruction by DoS attack of an extremist website, ansar- Anonymous also started a Twitter campaign #OpCharlie; paradoxically, the group reports that Twitter administrators have twice deleted their burgeoning following on @OpCharlie handles. #OpCharlie has leaked a list of Islamic State recruiters and go- betweens the group uncovered on and it has acquired more than 900 links to IS- linked accounts, websites and assorted online material, which it then hacks or denounces to service providers.

The most recent action this had led to: