Two people have been arrested in the UK for using another person's wireless internet access without permission. Neither was charged but both were cautioned for dishonestly obtaining electronic communications services with intent to avoid payment.

Advert: Free OUT-LAW breakfast seminars, Protecting your name on the net; and Overseas transfers of personal dataBoth people, a man and a woman, were arrested in Redditch in Worcestershire in two unrelated incidents weeks apart. Local police said that residents should make sure their wireless networks are encrypted to avoid others using their systems.

On Saturday police were called to a house because a man was sitting inside a car using a laptop computer with cardboard around his windows. Suspicious neighbours called the police, who found that he was using the wireless internet signal from one of the houses.

Using someone else's wireless internet service without their permission breaks the Communications Act, which prohibits dishonestly obtaining a communications service.

Communications Act 2003, section 125

Dishonestly obtaining electronic communications services

(1) A person who- 

(a) dishonestly obtains an electronic communications service, and 
(b) does so with intent to avoid payment of a charge applicable to the provision of that service, 

is guilty of an offence.

While many people may not mind someone using some of their bandwidth, allowing someone else to use a network presents a risk for the network owner.

Struan Robertson, editor of OUT-LAW.COM and a technology lawyer with Pinsent Masons, said: "The illegal acts of a stranger, such as hacking or visiting sites containing child pornography, will be traced to the network owner. That owner stands a good chance of losing his computer while it undergoes forensic examination to clear his name. But the worst-case scenario is to be wrongly accused of the crime."

Officer Tony Humphreys of West Mercia Police said: "Wireless networks don't stop at the walls of your home – and so without the necessary protection, your neighbours or people in the road outside may be able to connect to your network. This might slow down your internet service, or more importantly, your internet connection could be used for unlawful purposes."

"We want people to be aware that this is possible and to be vigilant themselves regarding their own broadband connections," said Humphreys.

The second Redditch case involved a woman who was arrested for similar activity last month. She was also cautioned but not charged.

Such cases are still relatively rare, and many users are not aware that using other networks is against the law.

In 2005 Gregory Staszkiewicz was fined £500 and sentenced to 12 months' conditional discharge for the same offence in London's Isleworth Crown Court.

Police said that wireless internet users should follow their ISP's instructions on how to secure their home networks.