On July 1, 2016, it was reported that hacker collective Anonymous was launching #OpIstanbul against ISIS in response to a suspected ISIS terrorist attack in Istanbul, Turkey that had left 44 dead. In a video posted online shortly after the attack, Anonymous promised to relaunch cyber-attacks against ISIS. Similar operations carried out by Anonymous in the past have typically involved finding and reporting ISIS social media accounts and having them suspended.
Source: Softpedia.com, July 1, 2016.