New research has revealed that our online privacy is not protected after we delete our social media accounts. In fact, our behaviors are predictable from the social media data of as few as eight or nine of our friends.
The study, by researchers from the University of Adelaide in Australia and the University of Vermont in the United States and published in the journal Nature Human Behaviour, found that even when people have deleted their accounts, they can be profiled from the information drawn from their friends' posts.
The universities said this is the first study to determine the extent to which information about individuals is encoded in their interactions with friends.
"Effectively, it shows that there is no place to hide on social network platforms," said co-author Dr Lewis Mitchell, senior lecturer in applied mathematics at the University of Adelaide's School of Mathematical Sciences.
"Telling people to delete your account in order to protect your privacy is not enough, as profiling information such as someone's political affiliations or leisure interests can be determined by your friends' posts. It's like listening in on one end of a phone call. Even though you can't hear the person on the other end of the line, you can still find out a lot of information about them from the one-sided conversation you can hear," he said.
During the study, researchers analysed the content of more than 30 million Twitter messages using information theory from mathematics and probability to test the predictability of individuals' behaviour based on the text that they publish online.
This analysis showed that up to 95 per cent of the potential accuracy for an individual is achievable using data from their friends alone. And data from eight to nine friends was enough to obtain predictability comparable to that using only individuals' data.
"Many people know they are giving out access to their information when choosing to use an online platform but they think it's only information about themselves," said co-author Dr Jame Bagrow who is assistant professor, mathematics and statistics at the University of Vermont.
"But it's not an individual choice – they are also giving away information about their friends," he said.
Meanwhile, the University of Adelaide's Dr Mitchell said there are benefits of being able to predict behaviour as social media platforms use this principle to target information so users receive posts that they are interested in.
"But of course there is a dark side as well, such as the potential for the creation of 'filter bubbles.' For instance in a political debate, people may be only exposed to one type of information and may not receive any opposing views," he said.