Jihad has hit cyberspace. The Cyber Caliphate, hackers apparently aligned with ISIS, took control of Twitter and YouTube accounts belonging to the U.S. Central Command yesterday. “American soldiers, we are coming, watch your back,” said one tweet. The hackers posted phone numbers of military brass, as well as pro-extremist videos on the military’s YouTube channel. Officials say the attack – which lasted 30 minutes – didn’t compromise classified information or threaten operations. But it did raise concerns about the military’s readiness on the technological front.