Did you know that websites can see if you are currently logged into Twitter, Facebook or Google+. Tom Anthony wanted to determine whether it would be possible to track which social networks a website visitor is logged into at the time of their visit.
Facebook provides an API for developers which can be used to find out about the login status of website visitors. You must have seen about that “Like box” plugin which displays your friends name when you’re signed-in and also determines whether you have already liked that page or not.
For Twitter and Google+, Tom needed to find a different way that was cross-browser compatible. He came up with a very clear idea. Basically he requested a file that require users to be logged in to view it. For e.g. there are some images that would be displayed to the user, only when the user is logged in. If the user is not logged in, then the page would be redirected and the user would be prompted to login first, before viewing that requested page.
To check this script, you can try out the status detector demo page. Just visit the URL and results will be automatically displayed. While testing, the results are perfect as they should be. In the above image, you can see whether I was logged into Twitter, Facebook, Google and Goole+. This script works on Firefox, Chrome, IE versions 7 and up, Safari and Opera.
To know more about the script, you can visit Tom’s blog as he has explained about this code with examples. To stay protected from being analyzed, users can logout of the services when leave the sites. Some users don’t click on the log-out button and remain logged in always, but with this simple trick, anyone can determine the status of your social networks.
This method can be exploited for good and bad. Good thing is that a website can present options based on the social networking sites the user is logged into. Or to further personalize the visitor’s stay by presenting social buttons. The bad side is that this can also be used for illegitimate purposes and ultimately harms user’s privacy.