Unique "usernames" for Ebay, Facebook etc. can be tracked by criminals, spammers etc.

French security academics developed a system that cross-referenced publicly-available data from several major websites to build up detailed profiles of real people.

The team harvested almost 10 million usernames from Google, eBay and MySpace.

Using statistical analysis techniques they showed that it is possible, to a high degree of certainty, to track about half of internet users across the internet based on only their username. They also showed that the more unique - the more entropy it has - the username, the more likely it is that it can be linked to a real person.

"For example, by matching a Google profile to an eBay account one could send spam emails that mention a recent sale."

The researchers argue that such targeted phishing emails would trick more people into clicking on malicious links that allow criminals to take control of computers.

Such profiling methods could also be used by unscrupulous online marketers to gather data about individuals' interests without their knowledge or consent.

To combat the potenital threat, the researchers suggest trying to use different usernames on different websites. The team have created a tool to allow internet users to test how unique their usernames are, to "allow them to take an informed decision on whether to change their pseudonym for their online activity they wish to remain private."

Check this link to see how unique your username is:
http://planete.inrialpes.fr/projects/how-unique-are-your-usernames/


Links:http://arxiv.org/abs/1101.5578
http://www.telegraph.co.uk/technology/news/8326598/Unique-usernames-allow-spammers-to-track-you.html