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.