Researchers at the University of Cambridge have created an online tool that can guess almost everything about you just by analyzing your Facebook likes.

The app works by comparing your Facebook likes to those of millions of other users. You need to give it permission to access your account, and once it does it runs your “digital footprint” against millions of other accounts and results from tens of thousands of personality tests. It also puts your personality on the so-called “Big 5” spectrum of traits: openness, conscientiousness, extroversion, agreeableness and neuroticism.

Using that information, the tool can guess nearly anything about you, including your age, gender, sexuality, political beliefs and even level of intelligence.

While this app is creepy enough on its own, its ultimate application may be even more troubling; according to The Washington Post, Cambridge created the app to advertise its technological capabilities to private companies. Meaning that very soon, advertisers and marketers could be using similarly creepy apps to analyze your personality.

But the real issue this app exposes is more insidious: even the smallest bit of information you share on Facebook can be used against you. What could seem tinier and more insignificant than liking a page? And yet that simple act can still encroach on your privacy.