The US National Security Agency (NSA) has installed software in about 100,000 computers around the world, enabling the spy agency to conduct surveillance on those machines and provide a "digital highway for cyber attacks", the New York Times reports.
The majority of the software is inserted into the systems by gaining access to computer networks; however, the NSA has also used "secret" technology that enables it to access and alter data on PCs, even if they are offline.
The technology, which has been used by the NSA since 2008, relies on a covert channel of radio waves transmitted from tiny circuit boards and USB cards that have discreetly been inserted into computers.
The New York Times claimed - citing US officials, IT experts and documents leaked by former NSA contractor Edward Snowden - that "in some cases, they are sent to a briefcase-size relay station that intelligence agencies can set up miles away from the target".
This enables the US intelligence agencies to crack into computers that adversaries and partners have disconnected from the internet in an attempt to make them spy-proof.
The programme, called Quantum, has targeted units of the Chinese Army, which the US has continuingly accused of conducting cyber-attacks on the US military, as well as industrial targets.
Russian military networks, systems used by the Mexican police and drug cartels, EU trade institutions and America's supposed allies Saudi Arabia, India and Pakistan have all been targeted by the programme. The report claims that the NSA "has been successful in inserting software" into these networks.
But there was no evidence, the Times said, that the NSA had installed software or used the "secret" technology inside the US.
President Barack Obama is expected to address the US on Friday on a number of new guidelines that he hopes to put into place to curtail official surveillance. People briefed on his announcement told the Times that he plans to increase limits of access to bulk telephone data, call for privacy safeguards for foreigners and propose the creation of a "public advocate" to represent privacy concerns at a secret intelligence court.