Privacy-conscious fans of Pink Floyd may never use the internet in the same way again.

A new Firefox add-on, dubbed Dark Side of the Prism, automatically plays tracks from the seminal 1973 album whenever a user visits sites, such as Google or Facebook, embroiled in the scandal over the National Security Agency's (NSA) snooping programme.

For example, users visiting Guardiannews.com would not hear any beguiling psychedelic rock. But those surfing Bing, Google, Facebook or Yahoo would be served up a healthy dose of Floyd noise.

The idea – according to its creator, 28-year-old developer and artist Justin Blinder – was to "create some sort of ambient notification that you are on a site that is being surveiled by the NSA."

About 50 people have downloaded the add-on in the few days since it was released, he says. It only took four hours to build from his makeshift office in New York.

"I was really interested in the fact that, although the Prism leaks were a shock to many of us, we pretty much already kind of know we're being surveiled a lot of the time and giving away so much data," he says.

Why did he choose Pink Floyd for the backing track? "I just Googled 'Prism' and the [Dark Side of the Moon] cover came up," he says, and because the music is unintrusive. "I didnt want it to be too jarring because a lot of us seem to be giving in to being surveiled on a daily basis. I feel like people already know that. I didn't want it to be alarming."

Blinder now hopes Floyd fans will help match Dark Side of the Moon songs to appropriate internet firms. "On the run", anyone?