Nearly half of home wi-fi networks can be hacked in less than five seconds, according to a study carried out across the UK.
Of the 40,000 networks identified across six cities, just under 20,000 had no password or the most basic form of security encryption, the research for card protection and insurance company CPP found.
In the “ethical hacking” experiment, researchers spent half an hour in each city using freely-available software to use as many unsecured wireless connections as possible.
Nearly a quarter of the private networks (9,249) had no password, despite 82% of Britons saying their network is secure.
But the study found even password-protected networks were not secure, with hackers able to breach a typical password in seconds.
Hackers were also able to “harvest” usernames and passwords at a rate of 350 an hour when sitting in town-centre coffee shops and restaurants.
CPP identity fraud expert Michael Lynch said: ”We urge all wi-fi users to remain vigilant and ensure their networks are secure.”