The FBI, DHS and United Kingdom cyber intelligence agency NCSC have jointly accused Russian-based attackers of having engaged in trying to compromise routers, switches and firewalls around the world to hijack the Internet's infrastructure.
The advisory says network devices are ideal targets because nearly all network traffic passes through them.
This could be used be used to mount a future offensive, it warned.
Though the governments are not sure how many devices have been compromised by the hackers nor what the objective is, the targeting affects millions of devices globally, U.S. officials said on a call with reporters Monday morning.
Officials said they had "high confidence" that the Russian government was behind the campaign. Attackers also sought to undermine the firewalls and intrusion detection systems organisations used to spot malicious traffic before it reached users.
This is because if the reports are to be believed, Russian Federation has apparently been hacking routers in homes around the world.
What no-one is quite sure of is whether this creates a deterrent a bit like mutually assured nuclear destruction in the Cold War.
Officials said that Kremlin-backed aggressors have accessed computer routers around the world as part of a cyber espionage campaign that targeted government agencies, businesses and critical infrastructure operators.
In addition, Mr Joyce said, many different organisation had come under attacks for months at a time in a bid to scoop up valuable intellectual property, business information or to get at their customers.
The chief of Britain's National Cyber Security Centre (NCSC) based at GCHQ in Cheltenham, Glos, said Russian Federation was "our most capable hostile adversary in cyberspace" and that "dealing with their attacks is a major priority" for British and American spooks.
"Many of the techniques used by Russian Federation exploit basic weaknesses in network systems", said Mr Martin.
The full alert contains indicators of compromise for the attacks, technical details on the tactics, techniques and procedures as well as contextual information regarding observation of the attacks.
The advice given to firms has included ways to configure their systems correctly and how to apply patches to address hardware vulnerabilities.
No sanctions or penalties were announced Monday, and the alert is unrelated to expected sanctions on Russian Federation in coming days, though Joyce reiterated that "all elements of U.S. power are available to push back" on such hacking efforts.
BRITAIN is braced for cyber warfare attacks by Russian Federation that could send services such as healthcare, transport and utilities into meltdown.
"The UK government will continue to work with the U.S., other worldwide allies and industry partners to expose Russia's unacceptable cyber behaviour, so they are held accountable for their actions", Martin added.