British spies are developing an offensive cyber capability to attack terrorists, hackers and rogue states, finance minister George Osborne said on Tuesday after warning Islamic State militants wanted to launch deadly cyber attacks of their own.
Osborne said Islamic State fighters were trying to develop the ability to attack Britain's infrastructure such as hospitals and air traffic control systems with potentially lethal consequences.
In response to this threat and others, Britain was creating its own offensive cyber capability so spies could launch counter attacks, he said.
"We will defend ourselves. But we will also take the fight to you," Osborne said in a speech at Britain's GCHQ eavesdropping agency.
"Strong defenses are necessary for our long-term security. But the capacity to attack is also a form of defense."
He said Friday's attacks in Paris, which killed at least 129 people and were claimed by IS, had underscored the need to improve Britain's protection against electronic attack.
ISIS was already using the Internet for propaganda, to radicalize people and for planning purposes, said Osborne, Prime Minister David Cameron's close ally.
"They have not been able to use it to kill people yet by attacking our infrastructure through cyber attack," he added. "But we know they want it and are doing their best to build it."