British security services jammed ISIS drones as part of an operation against the terrorist group, the chief of the UK's surveillance service said. Operatives in Syria and Iraq blocked the extremists' communications during firefights by disrupting their mobile phone signals. It is the first time that British authorities revealed the use of "offensive cyber" methods in operations against the extremists. "When adversaries like Daesh overstep the line, then they need to expect us to contest it [in cyber space] too," Jeremy Fleming, director of Government Communications Headquarters (GCHQ), said, using a pejorative Arabic term for the extremists. British special forces and GCHQ operatives were sent to support the Iraqi military and Syrian Democratic fighters against ISIS by using drones. “We piloted some early technologies to disrupt ISIS’s use of some pretty basic drone technology which was causing us a problem,” he told Sky News. “We used cyber techniques to affect how a drone operated.” The British operation also allowed containment of ISIS propaganda. Social media accounts were blocked, computers hacked and databases destroyed. The number of violent terrorist videos, which were used for recruiting, was heavily reduced. “We prevented their propaganda, both through physical actions on the battlefield but also remotely getting to … the places that they stored their material,” Mr Fleming said. In addition, British operatives targeted ISIS devices such as mobile phones and laptops to prevent them from sending and receiving orders. Frontline fighters were misdirected. A senior military official suggested that some ISIS troops became so demoralised after being cut off from their headquarters that they dropped their weapons and fled the battlefield. "We wanted to ensure that when they tried to co-ordinate attacks on our forces, their devices didn't work, that they couldn't trust the orders that were coming to them from their seniors," the UK’s head of strategic command, Gen Sir Patrick Sanders, said. "We wanted to deceive them and to misdirect them, to make them less effective, less cohesive and sap their morale. “But you can't just do that in cyber space. You have to co-ordinate and integrate that with activities that are going on the ground, whether it's from our own forces, special forces and others." Mr Fleming said coalition forces used the element of surprise by disrupting ISIS battlefield communications from 2016 onwards. The success of the counter cyber operation led to Britain setting up the National Cyber Force, which is run jointly by GCHQ, the armed forces, and MI6, its foreign intelligence service. The force not only targets terrorist groups such as ISIS, but also internet espionage by countries such as Russia and China. Mr Fleming declined to say how offensive operations had been used against other states but said it was “available to governments to use in that context”.