The idea is the brainchild of Aram Bartholl of EYEBEAM, an experimental tech agency combining art with modern computing technology. Bartholl was inspired by the Cold War-era espionage technique of hiding sensitive information in plain sight -- say, behind a loose brick or under a creaky floorboard.
But what presumably started as an overkill way for Bartholl to hide his pornography has since blossomed into a global trend, with at least 1,500 known installations around the world, featuring anything from cute cat pictures to recipes to instructions on how to build bombs.
And actual bombs, maybe.
As far as we're aware, no horrific viruses have spread through the project, but there have been enough terrorist manifestos and crystal meth recipes to draw the attention of police.
Uh ... nobody tell the police about the internet. They'd have a fit.