Dr Darren Mundy, lecturer in digital media at the University of Hull Scarborough campus, warns intelligent phishing, where people try to identify customers' bank details or passwords typically through emails, poses the next big threat to internet security.

He said: "At the moment phishing tends not to be targeted well, so most people just delete these kind of emails. But it is getting more clever and the amount of internet fraud caused by phishing is on the up.

"Nowadays there is technology which can track your movements across the internet, for example from your bank website to an online bookstore or clothing store.

"This information can be used to con people into handing over their details, saying there is a problem with a recent transaction from an online store for example. From there, fraudsters can illicit bank details and passwords to gain access to financial accounts."

Dr Mundy said people do not realise how easy it is for their information to be stolen.

He said: "There are many computer programmes out there which can easily decrypt what you would think is secure information, such as passwords and credit card details."

Dr Munday added that, once hackers have the details, they can sell them on to criminals for huge sums of money.

He added: "The worry is that because internet thieves often take small amounts from many accounts, sometimes well after the details have been stolen, consumers may have no idea it is happening."

Last year shoppers spent £15.2bn in the three months leading up to Christmas and this year is expected to be even bigger.

In 2007 internet fraud was estimated to total £290.5m.

Dr Mundy is advising people to use stores which have secure trading and a privacy policy on their sites.

People should also check that their own internet software security programmes are up to date.