The UK's key computer systems are being targeted by Trojan software apparently originating from the Far East, according to the National Infrastructure Security Coordination Centre (NISCC).

Both the UK government and private companies are being targeted, and an NISCC bulletin lists 76 Trojan programs that have been detected. The organisation claims that the IP addresses on the emails often come from the Far East.

"Trojan capabilities suggest that the covert gathering and transmitting of otherwise privileged information is a principal goal," stated the bulletin.

"The attacks normally focus on individuals who have jobs working with commercially or economically sensitive data."

The bulletin also warned that firewalls and antivirus software do not protect against the Trojans as they can be modified by security code to avoid signature traces.

"We see more than a dozen new pieces of malware capable of stealing highly valuable and sensitive information every day," said Carole Theriault, security consultant at Sophos.

"Trojans which allow unauthorised remote access to a computer pose a serious risk to all businesses."

The malware gets onto systems via spam emails containing .exe, .chm, .rar or .zip files at target systems.

The recipient is then tricked into opening the attachment and the code either logs keystrokes and send them to a third party or allows complete remote control of the infected PC.

"Because of the nature of the threat we only get to see a small part of what's there," said Steve Withers, managing director at networking security company Radware.

"If you call up Barclays bank they're not going to tell you they got hacked. It's predominantly a government problem but it's something that affects us all at the end of the day."