Over half of UK internet users have admitted using other people's Wi-Fi networks to piggyback onto the internet.

A recent survey by security firm Sophos found that 54 per cent of respondents had used someone else's wireless internet access without permission.

Many internet-enabled homes fail properly to secure their wireless connection with passwords and encryption, allowing passers-by and neighbours to 'steal' their internet access.

Although most businesses have security measures in place to protect their Wi-Fi networks, Sophos warned that remote users working from home could prove a weak link in corporate defences.

"Stealing Wi-Fi internet access may feel like a victimless crime, but it deprives ISPs of revenue," said Graham Cluley, senior technology consultant at Sophos.

"If you've hopped onto your next door neighbour's wireless broadband connection to illegally download movies and music from the web, chances are you are also slowing down their internet access and impacting on their download limit.

"For this reason, most ISPs put a clause in their contracts ordering users not to share access with neighbours. But this is very hard to enforce."

Sophos recommends that home owners and businesses set up their networks with security in mind, using strong encryption to prevent eavesdropping and the potential theft of usernames, passwords and other confidential information.

"If you are not encrypting your wireless communications it is easy for cyber-criminals to snoop on what you're doing, whether it's surfing the internet or remotely accessing work documents," warned Cluley.

"They may even be able to infect your computer with malware designed to commit identity theft. It is essential that your Wi-Fi connection is encrypted and that you have not chosen a password for your router which is easy to guess or crack.

"The problem is that a lot of Wi-Fi equipment is not properly configured when it comes out of the box, or is a headache to set-up."

A 39 year-old man was arrested in August on suspicion of stealing a Wi-Fi connection when he was found using a laptop outside a house in Chiswick in west London.

The first case of Wi-Fi theft in the UK to make it to court was in 2005 after an Ealing man was arrested for stealing Wi-Fi from a neighbour. He was given a 12-month conditional discharge and fined £500.