An estimated 2.93 million people managed to access an illegal online broadcast of Floyd Mayweather's 10-round victory over Conor McGregor in Las Vegas, online security experts have claimed.
Irdeto, a digital security company, says that the fight - only available on pay-per-view, for which viewers in the US had to pay up to $99.95 - was nevertheless made available for internet users through social media channels such as Facebook, YouTube, Periscope and Twitch.
Over 200 such streams were identified by Irdeto, the majority of which came via social media rather than the illegal streaming sites that have traditionally hosted the broadcasts.
Periscope - a live mobile video streaming application - itself became a trending topic on social media, as users desperately tried to track down active streams of a fight that costed £19.95 to watch on Sky Sports Box Office in the UK.
So-called "digital Robin Hoods" paid the subscription, only to make their stream available to anyone who had the link.
On just one day last week, Irdeto found more than 40 adverts promoting illegal streams for the Las Vegas event.
"Live sports are a cornerstone of global piracy, with thousands of sites providing illegal content attracting millions of viewers," said Rory O'Connor, senior VP of cybersecurity services at Irdeto.
"When combating live sports piracy, speed in disrupting piracy is essential. By identifying and stopping pirate streams in real-time through specialised knowledge and technology, content owners and operators are able to protect revenue and deliver a greater user experience."