ap photo Elon Musk speaks at the SATELLITE Conference and Exhibition in 2020, in Washington. Musk posted video Wednesday showing him strolling into Twitter headquarters ahead of a Friday deadline to close his $44 billion deal to buy the company.

Twitter’s unending fight against spam accounts is now a problem for new owner Elon Musk, who pledged in April to defeat the bot scourge or “die trying!”

He later cited bots as a reason to back out of buying the social platform. Now that the billionaire has completed the deal, he’s faced with the task of delivering on his promise to clean up the fake profiles that have preoccupied him and bedeviled Twitter since long before he expressed interest in acquiring it.

The challenge carries high stakes. The bot count matters because advertisers — Twitter’s chief revenue source — want to know roughly how many real humans they are reaching when they buy ads. It’s also important in the effort to stop bad actors from amassing an army of accounts to amplify misinformation or harass political adversaries.

“The bigger picture in my mind is: How do we make Twitter a better place for everybody,” said bot-counting expert Emilio Ferrara, who worked over the summer to investigate the problem for Musk. He cited the “value of the platform as a societal experience, as a collective place to have civilized discourse and talk freely without interference from nefarious accounts,” or scams, spam, pornography and harassment.

To find out just how bad the bots are, Musk hired Ferrara and other data scientists to investigate. At the time, he sought to prove that Twitter was misleading the public when it said fewer than 5% of its daily active users are fake or spam accounts. If Twitter lied or withheld crucial information about the bot count, Musk could argue that he was justified in terminating the $44 billion agreement.

Ferrara, an associate professor of computer science and communications at the University of Southern California, said he had no real interest in whether Musk ultimately ended up owning the platform.

Instead, he hoped that “any findings would be able to help improve the platform,” Ferrara told The Associated Press, speaking for the first time about his planned role as Musk’s expert trial witness.

The question now is what Musk will do with that information. Ferrara’s presentation — some 350 pages of analysis and supporting documents — is locked up in confidential court filings, and he said he can’t disclose his conclusions.

Twitter’s former leaders and its lawyers said Musk wildly exaggerated the problem because he had buyer’s remorse. Precise counts are “almost impossible” because any bot estimate is based on assumptions that can lead to bias, said Filippo Menczer, a researcher who was not working for either side in the dispute.

“Nobody knows exactly how bad the problem is,” said Menczer, director of Indiana University’s Observatory on Social Media. “I would guess it’s not as bad as Musk said and not as good as Twitter claimed.”

Many experts also doubt Musk’s ability to easily make improvements, which he’s suggested would rely on using algorithms to track and remove fake accounts and implementing new measures to “authenticate” real people.

Earlier this month, Ferrara was preparing to travel to the East Coast to testify in Delaware, where Musk was defending against Twitter’s lawsuit asking a court to force him to close the deal. But two weeks before the scheduled Oct. 17 trial, Musk changed his mind and said he would go ahead with the $44 billion acquisition. It closed Thursday.

Most legal experts didn’t think Musk had much of a case. The court’s head judge seemed likely to side with Twitter based on the specific terms and conditions of the April purchase agreement.

But that’s not to say Musk didn’t have a point about the bots, according to Ferrara and other researchers hired by Musk’s legal team.

The analysis firm CounterAction, which worked with Ferrara, said it concluded in a July 18 report submitted to the court that Twitter’s spam rate for monetizable accounts — those of value to advertisers — was at least 10% and could be as high as 14.2%, depending on how the rate is measured.

Trevor Davis, the firm’s founder and CEO, said that analysis was based on a “firehose” of internal data that Twitter gave to Musk, but the company declined to provide additional data sought by Musk’s team.

“We expect that access to the withheld data would reveal an even higher true spam rate,” Davis said in a prepared statement.

Musk has long been preoccupied with Twitter spambots promoting cryptocurrency schemes, in part because as a celebrity user with more than 110 million followers, he sees a lot of them. Some scammers have opened accounts mimicking Musk’s name and likeness to try to get people to think he’s endorsing something.