UK authorities are drawing a battle line in the wild world of wireless internet.

Two people have been arrested and officially warned for 'piggy-backing' someone else's wi-fi internet connection without permission.

A man was spotted by neighbours over the weekend sitting in a car outside of a home in Worcestershire using a laptop computer to connect to the Internet.

A similar incident last month saw a 29-year-old woman arrested in the same area.

Both received an official caution from police which is one step short of prosecution.

The warning was for 'dishonestly obtaining electronic communications services with intent to avoid payment'.

Very few people have been arrested for piggy-backing in the UK.

West Londoner Gregory Straszkiewicz was the first person to be convicted of the offence in 2005.

He was fined €750 and given a 12-month conditional discharge.

This new crackdown sparked a lively ethical debate in Internet chatrooms over whether piggy-backing is immoral or harmless.

'If it travels through the air it is open season,' wrote one contributor, while another said: 'If it's out there unsecure and I'm not trespassing, it's fair game.'

Up to a quarter of home wireless connections are unsecured, according to a consumer finance Web site.

Businesses are also at risk. A survey of 320 companies by a London trade show found that 25% have no wireless security policy.