Dawn Telfer didn't worry about sharing her details online until someone stole more than just her identity. "I went home and logged on to my online accounts and I was more than £6,000 overdrawn," she says.

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Somehow, a criminal had accessed Dawn's two online bank accounts, applied for overdrafts in her name and transferred the money into a new account. It's not known exactly where the criminal got the information, but they could have found some useful starting points on Dawn's social networking site. "I did have a MySpace profile with my name, address, date of birth and personal information," she says. "There are probably other forums I put my information on as well."

It is possible to choose to keep your details private on MySpace or Facebook. However, some experts believe this should happen automatically - otherwise you're dangerously unprotected. The risks aren't just theoretical. Watchdog set up an experiment to see how much information online friends will unwittingly give away and what can be done with it.

We created a fictional character called Amba Friend and set up a Facebook account for her. Amba sent messages to 100 other Facebook users chosen at random, asking them to be her friend. Of those, 35 total strangers said yes.

One of her new friends was Scott Gould, a 23-year-old from Exeter. By making friends with Amba, Scott automatically revealed the personal information he'd put on Facebook.

Tom Ilube, an expert at keeping your details safe online, told Scott: "The first thing I found is that you've left your date of birth there for all to see. To a potential fraudster, that's a very good starting point."

Using this information, a criminal could find more details about Scott by doing a quick search of other publicly available websites. With these details, Watchdog applied for an online bank account and credit card as if we were Scott. Both applications were instantly accepted.

"I'm very surprised about what you managed to do," says Scott. "I didn't think it would be possible. I've seen with my own eyes what you've done with that little bit of information."

Facebook told Watchdog it takes the issue of privacy very seriously and continually strives to be a trusted environment where users can join networks that are reflective of their real-life communities.

It says users have a great amount of control on Facebook with their privacy settings. It encourages everyone to utilise their privacy settings, to accept friend requests only from those individuals they know and to report any suspicious activity to customer services.

Facebook says when Amba Friend's profile was identified as being in violation of Facebook's terms of use, her details were disabled within 72 hours.

MySpace told Watchdog the safety and security of all its users is its number one priority. Every page on MySpace has a link to safety tips, which make it clear you shouldn't post any information you wouldn't want the world to know, such as where you live.

MySpace has extra precautions for younger users and everyone under 16 is automatically given maximum security settings. It says anyone else can adjust their settings to a level that suits them.

ID Theft Protect expert Julian Evans suggests Dawn Telfer and anyone who has been a victim of this type of fraud do the following:

1. Never click on any link in an email from someone you do not know - be careful when clicking on a link from someone you do know too! Why? The link may install a virus which in turn may log your keystrokes - so if you do online banking for example be extra careful as your card number, passcode and registration number could be copied and then someone else has access to your bank!

2. By all means use a social community website - but make sure you hide your profile on sites like Facebook. To find out how to protect your Facebook profile: http://www.id-protect.co.uk/news.php?news_id=106

3. Lastly - if you publish information on the Internet it is nearly impossible to remove all of it! So be extra extra careful what you publish and where!

You have been warned. Happy cybersurfing folks!

ARE YOU AT RISK OF IDENTITY THEFT? FIND OUT NOW!