COMPUTER users who join "broadband Britain" are putting themselves at risk from a range of new viruses.
A report from a consumer watchdog said there had been a huge increase in "intrusive and malicious" viruses that can alter computer settings and even steal your credit card details.
The number of people using the internet via broadband almost doub
led in 2004: about 5.3 million now have access.
Which? magazine warned that it was easier for hackers to exploit because customers were always online.
The greatest threat is from spyware, a software that sneaks on to computers and spies on what users do online before relaying the information back to whoever created it.
Oliver Powley, a senior researcher with Which?, said: "Spyware started out in a fairly benign way. But now it is much more intrusive and malicious.
"In the last 18 months we have seen some very powerful spyware which can delve into your computer and default your homepage or, more sinisterly, hack into your computer and change your dial-up setting. So, instead of ringing Freeserve or a local rate number, your computer will dial up an expensive 0800 number at £5 a minute."
Spyware emerged from online advertising in the late 1990s. It was designed to track the websites users looked at and to tailor advertising shots to their PC. For example, someone downloading a lot of car websites would be bombarded with motoring adverts.
The Which? researchers consulted a variety of software programmers including a former hacker who now works to protect corporate IT systems.
"It’s easier nowadays," he said. "If you have the right book and the right software tools, which you just download, you could start hacking in 20 minutes.
"The corporates have been successful at protecting themselves; they have the resources. But an average home user cannot spend £20,000 buying software and hardware to protect themselves."
Another damaging development is "phishing", which uses spam or pop-up messages to deceive you into disclosing your bank account information, credit card numbers, passwords or other sensitive information.
It has been estimated that the use of malicious code and phishing scams to extract confidential account details from consumers has cost British banks more than £4.5 million over the past 12 months.
As well as broadband, it has never been easier or cheaper to set up a wireless computer network at home. But this, too, comes with problems.
Police arrested a man in Toronto last year who had been driving around searching for unsecured domestic networks which he then used to access paedophile websites via his Wi-Fi laptop.
If he had not been caught in the act, the trail of evidence would have led instead to the people whose networks he had hijacked.
According to the Sans Institute, which specialises in computer security, there are more than 2,500 software vulnerabilities found every year.
The Internet Services Providers’ Association says it is imperative that broadband users have an internet firewall - a software program or physical box that limits access to your computer’s internet doorways from other online PCs.
Malcolm Coles, the editor of Which?, said: "Broadband is a big hit with UK consumers, provided you’ve got the right ISP and the right security software. Not having security software while connected to the internet has been compared to driving without a seat belt."
