The barrage of information leaks, state-sponsored espionage and hacktivism related to the U.S. presidential election has had a mixed bag of effects on the race and voter confidence.

Hackers sympathetic to ISIS may lack the funding and talent of government-sponsored hackers, but they merit attention because of their promotion of physical violence and ability to incite others via social media to target individuals or groups. A report today by security company Flashpoint points out that while these groups are not official members of...