Social media platforms such as Twitter can be used to glean information about the preferences of former users by monitoring as few as eight of their one-time contacts

By Umberto Bacchi

LONDON, Jan 21 (Thomson Reuters Foundation) - Bad news for anyone coming off social media in the hope it will preserve their privacy. It won't.

Research published on Monday showed social media platforms such as Twitter can be used to glean information about the preferences of former users by monitoring as few as eight of their one-time contacts.

"You alone don't control your privacy on social media platforms," said Jim Bagrow, a mathematician at the University of Vermont who led the research published in the journal Nature Human Behavior. "Your friends have a say too."

Tech giants including Google, Facebook and Twitter have come under increased scrutiny over the way they handle users' personal information to target advertising.

Last year Facebook, the world's largest social network, was buffeted by revelations that British consultancy Cambridge Analytica had improperly acquired data on millions of its U.S. users to target election advertising.

Bagrow and his team used statistical models to analyse data from more than 30 million publicly available Twitter posts by almost 14,000 users.

They found that machine learning algorithms may be able to infer with up to 64 percent accuracy what word a user was most likely to write next, based on what he and the people he interacted most often with had previously published.

Accuracy levels dropped only three percent to 61 percent when the algorithms were fed with text posted only by friends, according to the study.

"There's no place to hide in a social network," study co-author Lewis Mitchell said in a statement.

Twitter declined to comment. Its global data protection officer Damien Kieran told the U.S. Congress in September the company believed privacy was a fundamental right.

From political affiliation to purchasing practices and favourite television series, information shared online by friends and contacts could potentially be used to deduce many aspects of a person's life, Bagrow said.

"Information is so strongly embedded in a social network that, in principle, one can profile an individual from their available social ties even when the individual forgoes the platform completely," the researchers wrote in the study.

Although the study focused on Twitter the same information could be gathered form posts on other social media, like Facebook, provided access to them, Bagrow said.

Facebook, which tailors content and ads based on user activity, said it does not create profiles about non-Facebook users.

Both Twitter and Facebook allow users to control and delete data and information related to their accounts.

(Reporting by Umberto Bacchi @UmbertoBacchi, Editing by Claire Cozens. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's and LGBT+ rights, human trafficking, property rights, and climate change. Visit http://news.trust.org)

Our Standards: The Thomson Reuters Trust Principles.