Russian state-sponsored hackers are seeking to hijack critical network infrastructure devices, US and British intelligence agencies say.
The alert details methods used to compromise the networking equipment used to move traffic across the net.
The US Department of Homeland Security said the hacking was part of a broad operation dubbed Grizzly Steppe, which DHS says comprises concerting cyberattacks by Moscow's civilian and military intelligence agencies.
This could be used be used to mount a future offensive, it warned.
"We have high confidence that Russian Federation has carried out a coordinated campaign to compromise. routers, residential and business - the things you and I have in our home", said Rob Joyce, the White House cybersecurity coordinator.
First, this type of effort has targeted millions of machines to spy on ISP customers, organizations and government agencies.
Compromised devices were used to look at data passing through them, added Mr Joyce.
These attacks target government, the private sector and critical infrastructure, as well as the Internet Service Providers (ISPs) providing support to these sectors, with attacks across the globe on network infrastructure devices including routers, switches, firewalls, Network Intrusion Detection Systems (NIDS).
Manchester United face Pogba dilemma
We are a team that in the last three matches [against] Chelsea , Liverpool and Manchester City , has won all of them. The outcome of that game meant that Manchester City were crowned Premier League champions.
So far, there has been relatively little sign of this in the United States or UK, although Russian Federation is accused of launching destructive attacks against Ukraine.
The alert came from the Britain's National Cyber Security Centre, DHS and the US Federal Bureau of Investigation.
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". Finally, the alert outlined what erratic hardware behavior should indicate a device has been compromised.
The advice given to firms has included ways to configure their systems correctly and how to apply patches to address hardware vulnerabilities.
Monday's announcement is the latest in a series of related moves by the Trump administration, which in recent months has publicly blamed Russian Federation for launching the NotPetya worm that's been characterized as the costliest and most damaging cyber attack in history.
"The UK government will continue to work with the United States, other global allies and industry partners to expose Russia's unacceptable cyber behaviour, so they are held accountable for their actions", Martin added.