Promoters are expected to earn up to $1 billion tonight from pay-per-view buys.

The Mayweather-McGregor fight is almost here. The boxing battle between Floyd "Money" Mayweather Jr. and UFC star Conor "the Notorious" McGregor is expected to start tonight at 9pm ET at the T-Mobile Arena in Las Vegas.

Millions are expected to tune in for the event on Showtime and elsewhere and pay up to $99 for the live video feed. Mayweather is being paid a $100 million fee and McGregor, $75 million. Overall, promoters are expected to earn up to $1 billion in pay-per-view revenue globally.

With so much money at stake, it's no wonder dozens of piracy sites have thrown their hats into the ring, offering the fight either for free or for a much cheaper fee. In response, Showtime has convinced a federal judge to issue an injunction against the 44 sites it believes will show the fight Saturday night. The court ruling prohibits them from streaming the bout.

But whether this is just a body blow or amounts to a knock-out is anybody's guess. The listed sites in the injunction have gone dark for now. But pirate sites often spring up right before big events. The illicit sites turned on immediately before Mayweather's 2015 fight and victory over Manny Pacquiao, a truism that was not lost on Showtime.

"These unauthorized streams are provided for the commercial gain of the pirates, typically by charging a fee, advertising, or both," the company said in its lawsuit. (PDF)

Ars has reached out to some of the pirate sites' alleged operators (PDF) for comment and have not heard back. Many of them had been publicizing the fight before they went dark.

According to the judge's injunction:

"Defendants have not complied with Plaintiff's demands that they remove references to the anticipated infringement and refrain from streaming Coverage of the Fight, nor have they responded to Plaintiff’s Advance Notice of Potential Infringement," US District Judge André Birotte Jr. wrote (PDF) in the injunction.

"Even if the Defendants were to halt their promotion of their unauthorized live stream by temporarily shutting down their network of sites, these sites could be reactivated minutes before the Fight begins, leaving Plaintiff with no remedy until after the damage has been done. If Defendants were to proceed with their anticipated unauthorized stream of the Coverage, they would violate exclusive rights owned by Plaintiff under the Copyright Act, including without limitation the exclusive rights of reproduction and public performance."

For the uninitiated, Mayweather is 49-0 with 26 knockouts. At age 40, he has returned from a two-year retirement to take on McGregor, 29, who is 21-3. McGregor is the UFC lightweight champion and perhaps the most-known name in professional mixed-martial arts. As of this writing, Mayweather was the Vegas betting favorite—at -375.

The fight is scheduled for 12 rounds and will be under standard boxing rules.