MI5 has warned UK companies that the Chinese government may have gained access to their computers with the intention of remotely monitoring their online activities.
A leaked document seen by The Sunday Times claims that Chinese security officials have been offering free computer devices that contain Trojan software to high profile business users in the banking, defence and energy industries.
The devices include camera equipment and USB memory sticks that have been given out at trade events.
Business users in public relations companies and law firms are also thought to have been targeted.
A call to the Department for Business, Innovation and Skills referred queries on the matter to the Cabinet Office, which said that it would not discuss leaked documents and could not offer any further clarification on whether businesses should be worried about the alleged surveillance.
However, a government spokesman referred anxious executives to the Centre for the Protection of National Industry for advice.
It is unclear how many businesses may have been affected by the Trojans, or how long the monitoring has been taking place.
Reports suggest that the MI5 document is 14 pages long and entitled The Threat from Chinese Espionage.
MI5's Centre for the Protection of National Infrastructure wrote the report a year ago and shared it with a restricted number of businesses.
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