Most of us understand by now that we’re being followed across the web. But how much do we know about how the smartphone apps we use track our every move? Thanks to tiny pieces of code that millions of developers…

In a tiny third-floor apartment in central London, the artist Anna Ridler was hunched over her desk. Next to the desk was a black PC tower whirring noisily and in front of her was a keyboard and a screen covered with a…