Over half of all computer viruses, trojans and malicious code are created to steal sensitive information and make money, according to research released today.

A report by IT security firm Symantec shows that 54 per cent of the most common malware samples discovered in the last six months were written by criminals to extort money and steal identities.

The use of spyware and other key-logging tools increased by 44 per cent during that period as crime gangs looked to steal email addresses, cached log-on details, financial information and sensitive corporate data for monetary gain.

Phishing attempts - which use social engineering methods to trick users into giving up passwords, credit card details and other financial information - also increased by over 366 per cent between the period of July to December last year.

Symantec detected more than 33 million phishing attempts against per week against customers in December 2004 compared to a weekly average of nine million last July.

Some 25.2 per cent of compromised machines are located in the UK and being used to unknowingly distribute spam, virus and denial of service attacks, the report says.

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