An Israeli woman uses her iPhone in front of the building housing the Israeli NSO group, on August 28, 2016, in Herzliya, near Tel Aviv.An Israeli woman uses her iPhone in front of the building housing the Israeli NSO group, on August 28, 2016, in Herzliya, near Tel Aviv.

The Federal Bureau of Investigation and Apple are being pressed to provide information about the NSO Group, according to letters obtained by CNBC.

The New York Times reported earlier this year that the FBI had acquired technology from the NSO Group.

The Committee is examining the FBI's acquisition, testing, and use of NSO's spyware, and potential civil liberty implications of the use of Phantom against U.S. persons.

An investigation by a coalition of news outlets found that NSO's software was used to hack into the phones of journalists and activists. The report was denied by the NSO Group. The firm was blacklisted by the Biden administration a few months after the investigation was published because it knowingly supplied technology to foreign governments who used it to target dissidents, activists and journalists.

It's a spy tool that can be used to hack into Apple and Google phones without the victim having to click on a link. Vice News reported that the NSO Group had pitched a tool called Phantom to police in the U.S. According to The Times, the Israeli government granted a special license allowing Phantom to target U.S. phones, but only the U.S. government could buy the tool. The FBI was shown the tool by the company.

Jordan and Johnson wrote a letter to the FBI Director saying they found the FBI's acquisition of NSO spyware to be deeply troubling and presents significant risks to the civil liberties of U.S. persons.

According to the Times, the FBI bought and tested the technology before deciding against using it in the U.S. The FBI is being asked to hand over communications between the agency and the NSO Group or its subsidiaries about the agency's purchase, testing or use of NSO spyware and the potential legality of using Phantom against domestic targets.

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In their letter to Apple, Jordan and Johnson asked CEO Tim Cook to provide details about Apple's ability to detect when the NSO Group tools are used. The number of attacks that Apple detected from the tools is requested by the letter. It asks Apple for a staff level briefing about the company's communications with government agencies.

Zero days are flaws in Apple's code that it doesn't know about and hasn't patched yet. The NSO Group was sued by Apple in November for targeting its technology with the spyware, and Apple sought an injunction to prevent the NSO Group from using any Apple devices or software.

Security researchers have called for more transparency from Apple because of the company's preference for secrecy. It's not clear if the NSO technology has other ways to hack phones, though Apple patched a flaw used by Pegasus.

Requests for comment from Apple, the FBI and the NSO Group were not immediately responded to.

The FBI is looking at new technologies to combat crime and protect our civil liberties, not just to explore a potential legal use, according to a statement. We routinely identify, evaluate and test technical solutions and services for a variety of reasons, including possible operational and security concerns they might pose in the wrong hands.

The letters are on the ground.