Companies and government agencies in the U.K. are under attack by a series of Trojan horses that are working in conjunction to steal information, according to the National Infrastructure Secure Co-ordination Centre (NISCC).

The British agency, which protects 'critical national infrastructure' from electronic attack, is reporting that nearly 300 critical businesses and government departments in the U.K. have been the target of concerted Trojan horse attacks. Many of the attacks are thought to originate in the Far East.

The Trojans, which are delivered in email attachments or through links to Web sites, appear to be trying to gather and transmit 'commercially and economically valuable' information, according to a report from the NISCC.

''These electronic attacks have been underway for a significant period of time with a recent increase in sophistication,'' the NISCC said in an online alert. ''A number of open source and bespoke Trojans, altered to avoid anti-virus detection, have been used. The wide variety and constant evolution of the Trojans used appears to be an attacker strategy to identify the conditions needed to successfully penetrate a network.''

Analysts at Sophos, Inc., an anti-virus and anti-spam company based in the U.K., have been helping the U.K. government analyze the Trojans. Carole Theriault, a security consultant at Sophos, says using Trojan horses to steal information, and not simply to cause a nuisance, is a growing trend.

''We see more than a dozen new pieces of malware capable of stealing highly valuable and sensitive information every day,'' says Theriault. ''Trojans which allow unauthorised remote access to a computer pose a serious risk to all businesses. While it's worrying that the U.K.'s critical infrastructure could be at risk, this also serves as a reminder to all U.K. businesses that they must keep their systems secure to avoid confidentiality leaks. Every computer used for business must be protected with up-to-date anti-virus software and a firewall.''