Russia is targeting the home internet networks of tens of thousands of households in Britain to spy on them and mount mass cyber-attacks, GCHQ and the FBI have warned.
The security services in both the US and the UK said that they are "confident" that Russia is hacking into "residential routers" which people use to connect to the internet, providing them with a "tremendous weapon" against the West.
In an extraordinary joint statement, GCHQ and the FBI also revealed that Russia is preparing to mount cyber attacks on Britain's "critical infrastructure" including energy networks, the emergency services and the armed forces.
Authorities in the US and the UK revealed that Russia has been probing the cyber-defences to identify vulnerabilities that will "lay a foundation for future offensive operations".
They disclosed as a "man in the middle" by hijacking routers, enabling them to monitor all internet activity including emails, browsing history and passwords.
The National Cyber Security Centre, the FBI and the Department for Homeland Security in the US have warned that this "threatens our respective safety, security and economic well-being".
The security services yesterday issued a warning to Government bodies, large companies and "critical infrastructure providers" advising on ways that they can "mitigate" the threat posed by Russia.
Rob Joyce, the White House's cybersecurity co-ordinator, said: "We are pushing back hard. Cyber activity must be stopped and opposed at every turn. "We are confident that Russia has carried out a co-ordinated campaign to gain access to enterprise, small office routers and residential routers - the kind of things you and I have in our homes.
"We can't rule out the possibility Russia may intend to use these set of compromises for future offensive operations." Mr Joyce said that Russia is hacking into people's home networks when they use default passwords or in some cases no passwords at all.
The security are increasingly concerned that Russia may be hacking into people's home internet networks so they can hijack their computers and use them together as "botnets" to mount a mass cyber attack.
Howard Marshall, Deputy Assistant Director at the cyber division of the FBI, said: "Once you own the router, you own the traffic. You include the ability to monitor all traffic. It is a tremendous weapon. We will bring every tool to bear against them in every corner of cyberspace."
Ciaran Martin, head of the National Cyber Security Centre which is part of GCHQ, said there was proof that Russia had been attempting to hack into Britain's energy supply networks.
He said that "millions" of devices including laptops and mobile phones are being targeted by Russia around the World.
He said: “Many of the techniques used by Russia exploit basic weaknesses in network systems. The NCSC is leading the way globally to issue advice and automate defences at scale to remove those basic attacks, thereby allowing us to focus on the most potent threats.”
Security services have been tracking the activity of Russian hackers for over a year. The UK is working with America, its other allies and the technology industry to "expose Russia's unacceptable cyber-behaviour, so they are held accountable for their actions", said Mr Martin.