Over four million web users have had their Wi-Fi connection hijacked in the last year, says Moneysupermarket.com.

According to research by the comparison website, 19 percent of Brits don't password-protect their internet access at home. Furthermore, 24 percent said they didn't know Wi-Fi hijacking was possible.

Moneysupermarket.com said 15 percent of web users admitted to using someone else's web connection. The comparison website said Wi-Fi hijackers were most likely to use someone else's internet access to surf the web, although emailing, downloading large files and streaming content using service such as Spotify or the BBC iPlayer were also popular activities.

James Parker, broadband manager at moneysupermarket.com, said, "The consequences of hijacking can be severe. It's bad enough your neighbours can use your internet connection freely, but this becomes far more threatening if someone uses your connection for criminal or improper activity.

"If people aren't careful, they could unwittingly find a huge bill landing on their doorstep for going over the download cap imposed by their provider. More and more providers offer routers with broadband packages and the range of the signal is increasing. People need to be aware just how important protection is and the best way to go about it."

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See also: Two out of five at risk from Wi-Fi hijacking