The MI5 has warned UK banks that state-sponsored Chinese hackers could try to infiltrate their systems, according to the Times.
Britain's security agency sent an advisory note to UK banks saying that "electronic espionage attacks" could come from China.
Banks and law firms were among the 300 businesses that Jonathan Evans, the director-general of MI5, wrote to with the warning, after Rolls-Royce and Royal Dutch Shell were made victims.
Commenting on Mr Evans' move, Graham Cluley, senior technology consultant for Sophos, was quoted in the Register as saying: "Spying has been going on between countries for thousands of years, and it would be foolish to think that countries would not take advantage of computers and the internet to assist them in this.
"It is, however, unusual for a country to so openly accuse another of engaging in this activity - especially when it can be extraordinarily difficult to prove an attack is being sponsored by a government or is a lone hacker acting independently."
Some 30 per cent of malware created comes from China, with specialists working on software which steals login details.
In September, the Pentagon accused the Chinese of hacking into the US defence secretary Robert Gates' computer.
Although the UK's National Infrastructure Security Co-ordination Centre warned of Trojan attacks on computers in 2005, banks have now been put on high alert due to MI5's warning.
