Russian state-sponsored hackers are seeking to hijack critical network infrastructure devices, U.S. and British intelligence agencies say.
Britain's National Cyber Security Centre (NCSC), the FBI, and the U.S. Department of Homeland Security (DHS) issued a joint alert on April 16, warning that the global campaign could be escalated to launch future offensive attacks.
Moscow did not immediately comment on the allegations. It has denied previous accusations that it carried out cyberattacks on other countries.
The alert said the targets of the campaign were primarily "government and private-sector organizations, critical infrastructure providers, and the Internet service providers (ISPs) supporting these sectors."
"Russian state-sponsored actors are using compromised routers to conduct spoofing 'man-in-the-middle' attacks to support espionage, extract intellectual property, maintain persistent access to victim networks and potentially lay a foundation for future offensive operations," it said.
"They could be prepositioning for use in times of tension," Ciaran Martin, head of the British NCSC said, adding that "millions of machines" used to move traffic across the net were targeted.
White House cybersecurity coordinator Rob Joyce said the United States and its allies had "high confidence" that Russia was behind the campaign.
Compromised networking equipment were used to look at data passing through them, he also said.
Hackers also sought to undermine the firewalls and intrusion-detection system devices.
Britain and the United States said they issued the alert to help targets protect themselves and persuade victims to share information with government investigators.
"We don't have full insight into the scope of the compromise," Jeanette Manfra, a cybersecurity official for the DHS, said.
A British government spokesman called the global campaign of cyberespionage "yet another example of Russia's disregard for international norms and global order."
"The attribution of this malicious activity sends a clear message to Russia -- we know what you are doing and you will not succeed," the spokesman added.