Meta supremo  Mark Zuckerberg, was itching to get the lowdown on Snapchat's encrypted chatter.

Whenever someone asks a question about Snapchat, the answer is usually that because their traffic is encrypted we have no analytics about them," said Mark Zuckerberg in an email to three Facebook executives in 2016, unsealed in Meta's antitrust case on Saturday. "It seems important to figure out a new way to get reliable analytics about them... You should figure out how to do this."

So Meta created a crafty VPN called Onavo that's more like a double agent than a privacy pal.

Meta's boffins cobbling together some nifty "kits" for iOS and Android to eavesdrop on the competition. YouTube and Amazon got the same treatment, with Onavo users none the wiser that they were the bait in this cyber spy game.

Meta acquired Onavo from an Israeli firm over 10 years ago, promising users private networking, as most VPNs do. However, the service was reportedly used to spy on rival social media apps through tens of millions of people who downloaded Onavo. It gave Facebook valuable intel about competitors, and this week's court filings seem to confirm that. A team of senior executives and roughly 41 lawyers worked on Project Ghostbusters, according to court filings.

The group was heavily concerned with whether to continue the programme in the face of press scrutiny. Facebook ultimately shut down Onavo in 2019 after Apple booted the VPN from its app store.