The National Cyber Force’s existence has been publicly confirmed after months of speculation and a decade after the UK first began offensive cyber-operations.
It will counter threats from terrorists, criminals and hostile states.
MI6 officers will work alongside both the cyber-spy agency GCHQ and the military as part of a new unified command.
It has been up and running since April.
But it was only formally made public by the prime minister on Thursday.
The aim is that when UK armed forces go into combat, cyber-operations will be closely integrated with the traditional military.
One possible scenario would see operators hacking into enemy air defences to protect RAF missions.
But the force is not just about a high-end military capability.
It has been designed to operate day-to-day against wider threats.