By Chris Stokel-Walker

You can surf the dark web but you can’t always hide. People who want to keep their online activities secret will often use both bitcoin, which is tied to pseudonyms, and the Tor browser, which obscures your real movements. But if you’re not careful, all that hassle could be for naught.

By linking bitcoin wallets with transactions on the dark web, researchers at Qatar University in Doha were able to unmask 125 Tor users.

Supposedly secret activity on sites like The Pirate Bay …