The National Cyber Security Alliance (NCSA) has warned users of social networking sites such as MySpace and Facebook that they are vulnerable to cyber-crime.

A popular perception is that social networking is an activity enjoyed almost exclusively by teens. But the NCSA social networking research study, in association with CA, revealed that 48 per cent of social networking users are adults.

The research found that, although 57 per cent of people who use social networking sites admit to worrying about becoming a victim of cyber-crime, they are still divulging information that may put them at risk.

Around 74 per cent have given out some sort of personal information, such as their email address, name and birthday.

A further 83 per cent of are downloading unknown files from other people's profiles potentially opening their PC to attack.

"Although the general community thinks that most social networking users are teens, the CA/NCSA survey showed that the popularity of these sites is extending beyond young early adopters to other segments of the population," said Ron Texeria, executive director of NCSA.

"Those who frequent these sites should be aware that the data they share may make them prey to online attacks.

"Giving out a social security number, paired with a birthday and name, could provide enough for criminals to hack into financial records and compromise users' personal information."

But users of social networking sites are also engaging in other risky behaviour, such as downloading unknown files and responding to unsolicited emails and instant messages, all of which may lead to ID theft, spyware, viruses and other risks.

Of those who have access to a computer at work, 46 per cent engage in social networking at the office, potentially making the workplace vulnerable to online security threats.

The NCSA and the National Consumers League have established pointers to stay safe while on social networking sites: