One in four social network users are posting information that leaves them at risk of identity fraud, according to research from government-backed Get Safe Online.

While 88 per cent of internet users are demonstrating signs of vigilance by installing security software such as a firewalls, anti-spyware and antivirus, their behaviour online is putting them at increased risk of web-based crime.

One in four of the 10.8 million UK users registered on a social networking site have risked identity fraud by posting confidential or personal information on their profile. This information typically includes phone number, home address and email.

Some 13 per cent of social networkers have also posted information or photos of other people without seeking their consent, according to the research.

Younger users are the worst offenders. More than a quarter of 18-24 year-olds have posted information about other people without first securing their consent.

"The popularity of social networking and other sites means that we are much more open about ourselves and our lives online," said Tony Neate, managing director of Get Safe Online.

"Although some of these details may seem harmless, they provide rich pickings for criminals. Your date of birth and where you live is enough for someone to set up a credit card in your name.

"While most people would not give this information to a stranger in real life, they will happily post it online where people they do not know can see it. "

The research also pointed to the dangers of unsecured wireless networks, reporting that 7.8 million people in the UK leave their internet access open for anyone to use.