The advent of social networking Web sites like Twitter and Facebook has made private data online much more easily accessible. Tuesday's "Safer Internet Day" aims to make Internet users more aware of their online presence and the dangers it could pose. The European Union's cyber security body, the European Network and Information Security Alliance, or ENISA, is one of multiple organizations that supports Safer Internet Day.

ENISA spokesman Ulf Bergstrom talked to Deutsche Welle about the advantages – and dangers – of social networking Web sites and what users can do to protect themselves on the Internet.

DW: What do people need to look out for when using social networks?

Ulf Bergstrom: They should be careful about what they post online, because you never know who actually will use this information. Of course you should have fun and take use of social networks, and especially when you're doing mobile social networking. But you also need to be smart and clever, and don't post anything you can't live with all of your life. And that's of course not very easy for teenagers to think about. But really, this is about what their future potential employer may look at in ten years time, or in five years time, even. So you should not post sensitive information.

So basically, part of your message is don't mix business with pleasure. Is that correct?

That's entirely true. What we've seen lately are a lot of cases, notably also in the UK, where people have been using social networks...posted comments online about passengers from two airlines, negative comments about passengers, finally resulting in the dismissal of some certain staff members of one company because it was just not in line with company policy to criticize smelly passengers, for example. These things should not be posted online.

Are we speaking specifically about Twitter, about Facebook, or about all social networks entirely?

Actually all social networks. And this is the fantastic thing, in one sense, that we can meet people, share opinions, communicate in a totally different and new way and exchange information and ideas in a totally new manner. But at the same time there are also new risks, which you have to think about.

What can anyone do specifically to protect themselves?

Make sure that when you're doing mobile social networking and doing it when you're on the run, log out when you stop using it. Because you never know what will happen if your mobile phone were stolen – all the data, information, pictures, videos that are stored there – and somebody can use your name and steal your identity. And that would not be good for you, neither professionally nor privately.

Is this is a real, serious problem now that people are using their iPhones and their other mobile telephones more for Internet surfing?

Absolutely. And think about it from a company's perspective: If somebody posts live what is happening on Twitter all the time, or you say something, they may record it over the mobile phone and broadcast it all over the world. And suddenly that could cause, of course, huge damage for the corporate reputation. And that's something that managers really should be thinking about. How do we deal with this new world, these new tools? Which are great for one sense, but you also put yourself at risk if you don't have a company policy on how people can use social media.

Interview: Rick Demarest and Mark Caldwell (acb)
Editor: Andy Valvur