A newly released letter has formally acknowledged what was only briefly stated last month in a San Francisco courtroom: federal prosecutors have an open criminal investigation into Uber.

Late last month, as part of the proceedings in the high-profile and ongoing Waymo v. Uber trade secrets lawsuit, US District Judge William Alsup said that on November 22 he had received a letter from San Francisco-based federal prosecutors. It is very unusual for a judge in a civil case to be apprised of a pending criminal investigation involving one of the litigants.

In a separate November 28 letter sent to Judge Alsup, Acting US Attorney Alex Tse asked that the first letter not be made public. The judge unsealed both letters on Wednesday.

The first letter was signed by two prosecutors, Matthew Parrella and Amie Rooney. Those attorneys are assigned to the Computer Hacking and Intellectual Property (CHIP) Unit at the United States Attorney’s Office in San Jose.

"The presence of these particular prosecutors’ names on this letter, prosecutors from the office's computer hacking section, may suggest the government is pursuing yet another angle of investigation," Kathryn Haun, a former prosecutor who now teaches at Stanford University's Graduate School of Business, told Ars.

In other words, the letter could mean Uber and/or its current or former employees may be under investigation for possible crimes under the Computer Fraud and Abuse Act, a longstanding anti-hacking law.

Abraham Simmons, a spokesman for the US Attorney's Office in San Francisco, declined Ars' request for comment.

Separately, Uber is already reportedly facing inquiries into possible violations of the Foreign Corrupt Practices Act relating to its practices in a handful of Asian countries.

The November 22 letter refers to ex-Uber security official Richard Jacobs, who threatened to sue Uber after departing from the company in May 2017. That 37-page demand letter, which was filed by a Minnesota attorney on his behalf, has been described and quoted in court but has not yet been made public. In it, Jacobs said that he and his colleagues engaged in possibly criminal behavior.

"Mr. Jacobs further stated that Uber employees routinely used non-attributable electronic devices to store and transmit information that they wished to separate from Uber’s official systems," prosecutors wrote. "He surmised that any wrongfully obtained intellectual property could be stored on such devices, and that such action would prevent the intellectual property from being discovered in a review of Uber’s systems."

Curiously, while on the stand during evidentiary hearings held late last month, Jacobs repudiated some of what was in the letter, calling some language "hyperbolic." During the three days of explosive testimony, it was also revealed that Jacobs was paid $4.5 million by Uber to not file his lawsuit while his then-lawyer, Clayton Halunen, received $3 million.

In a separate filing, Judge Alsup said that barring any extraordinary objections, the Jacobs letter will be made public on Friday at 12pm Pacific Time.

The final pretrial conference has been scheduled for January 30, 2018, with the trial set to begin Monday, February 5, 2018.

Waymo v. Uber began back in February, when Waymo sued Uber and accused one of its own former employees, Anthony Levandowski, of stealing 14,000 files shortly before he left Waymo and went on to found a company that was quickly acquired by Uber. Levandowski, who refused to comply with his employer's demands during the course of this case, has since been fired. Uber has denied that it benefited in any way from Levandowski's actions.

Uber did not immediately respond to Ars' request for comment.