The two nations allege routers in government buildings as well as small offices could have fallen victim, while critical infrastructure and internet service providers could have also been compromised.
According to a joint statement between British intelligence, the Federal Bureau of Investigation, the White House National Security Council and Homeland Security on Monday, Russian "cyber actors" had compromised routers, which are used to connect computers to the internet, to breach security systems and steal information.
The goal of the announcement Monday was to warn corporations and individuals to protect themselves against attacks.
The statement (via Forbes) says Russian Federation is carrying out the operations "to support espionage, extract intellectual property, maintain persistent access to victim networks and potentially lay a foundation for future offensive operations".
"The current state of U.S. and United Kingdom network devices, coupled with a Russian government campaign to exploit these devices, threatens our respective safety, security, and economic wellbeing".
"We are pushing back and we're pushing back hard", said Rob Joyce, White House special assistant to the president and cybersecurity director.
"We don't have full insight into the scope of the compromise", said U.S. Department of Homeland Security cyber security official Jeanette Manfra.
The Pentagon has said Russian "trolling" activity increased 2,000 percent after the Syria strike.
Howard Marshall, who works in the FBI's cyber-division and who was on the conference call, said: "We will bring every tool to bear against them in every corner of cyberspace".
Mr Martin said authorities had been tracking the campaign for about a year and the tactics behind them for longer.
Australia said on Tuesday that up to 400 businesses had been targeted by suspected Russian state-sponsored cyber-attacks in 2017 but that there was no evidence of significant exploitation.
While representatives of the UK and the U.S. were united in strongly condemning the attacks, the Russian government has denied involvement. "The NCSC is leading the way globally to automate defences at scale to take away some of those basic attacks, thereby allowing us to focus on the most potent threats".
USA and British officials warned that infected routers could be used to launch future offensive cyber operations. "But unlike Russian Federation, we abide by the law, so anything we do would be proportionately done", said one source.