NEW YORK (CBSNewYork/AP) — The FBI now owns the proprietary rights to the method used to crack the San Bernardino gunman’s iPhone, a government official told CBS News.

The FBI said Monday it successfully used a mysterious technique without Apple Inc.’s help to hack into Syed Farook’s iPhone. Farook, along with his wife, died in a gun battle with police after they killed 14 people in San Bernardino, California, in December. The iPhone was found in a vehicle the day after the shooting; two personal phones were found destroyed so completely that the FBI couldn’t recover information from them.

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Apple software engineers — and outside experts – are puzzled about how the FBI broke the digital locks on the phone without Apple’s help. It also complicated Apple’s job repairing flaws that jeopardize its software.

The Justice Department’s announcement that it was dropping a legal fight to compel Apple to help it access the phone also took away any obvious legal avenues Apple might have used to learn how the FBI did it. The Justice Department declined through a spokeswoman to comment Tuesday.

It is a closely held secret how the FBI hacked the iPhone, but a few clues have emerged. A senior law enforcement official told The Associated Press that the FBI managed to defeat an Apple security feature that threatened to delete the phone’s contents if the FBI failed to enter the correct passcode combination after 10 tries. That allowed the government to guess the correct passcode by trying random combinations until the software accepted the right one.

It wasn’t clear how the FBI dealt with a related Apple security feature that deliberately introduces increasing time delays between guesses. The official spoke on condition of anonymity because this person was not authorized to discuss the technique publicly.

According to Ynet, the FBI was “reportedly using the services of the Israeli-based company Cellebrite in its effort to break the protection on a terrorist’s locked iPhone, according to experts in the field familiar with the case.

Cellebrite has not responded to the report.

Cellebrite is considered one of the leading companies in the world in the field of digital forensics and has been working with the world’s biggest intelligence, defense and law enforcement authorities for many years.

The company provides the FBI with decryption technology as part of a contract signed with the bureau in 2013.

Cellebrite’s technology is able to extract valuable information from cellular devices that could be used in criminal and intelligence investigations, even if the phone and the information it contains are locked and secure.

The FBI was reviewing information from the iPhone, and it was unclear whether anything useful would be found.

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Apple said in a statement Monday that the legal case to force its cooperation “should never have been brought,” and it promised to increase the security of its products. CEO Tim Cook has said the Cupertino-based company is constantly trying to improve security for its users.

The FBI’s announcement — even without revealing precise details — that it had hacked the iPhone was at odds with the U.S. government’s firm recommendations for nearly two decades that security researchers always work cooperatively and confidentially with software manufacturers before revealing that a product might be susceptible to hackers.

Those guidelines lay out a process about how and when to announce that commercial software might be vulnerable. The aim is to ensure that American consumers stay as safe online as possible and prevent premature disclosures that might damage a U.S. company or the economy.

As far back as 2002, the Homeland Security Department ran a working group that included leading industry technology industry executives to advise the president on how to keep confidential discoveries by independent researchers that a company’s software could be hacked until it was already fixed. Even now, the Commerce Department has been trying to fine-tune those rules to protect the digital economy. The next meeting of a conference on the subject is April 8 in Chicago and it’s unclear how the FBI’s behavior in the current case might influence the government’s fragile relationship with technology companies or researchers.

The industry’s rules are not legally binding, but the government’s top intelligence agency said in 2014 that such vulnerabilities should be reported to companies.

“When federal agencies discover a new vulnerability in commercial and open source software – a so-called ‘zero day’ vulnerability because the developers of the vulnerable software have had zero days to fix it – it is in the national interest to responsibly disclose the vulnerability rather than to hold it for an investigative or intelligence purpose,” the Office of the Director of National Intelligence said in a statement in April 2014.

The statement, which referenced new guidelines by the Obama administration on such disclosures, recommended generally divulging such flaws to manufacturers “unless there is a clear national security or law enforcement need.”

Last week a team from Johns Hopkins University said they had found a security bug in Apple’s iMessage service that would allow hackers under certain circumstances to decrypt some text messages. The team reported its findings to Apple in November and published an academic paper after Apple fixed it.

“That’s the way the research community handles the situation. And that’s appropriate,” said Susan Landau, professor of cybersecurity policy at Worcester Polytechnic Institute. She said it was acceptable for the government to find a way to unlock the phone but said the government should reveal its method to Apple.

Mobile phones are frequently used to improve cybersecurity in the private sector or federal agencies, for example, as a place to send a backup code to access a website or authenticate a user for a work system.

The chief technologist at the Center for Democracy and Technology, Joseph Lorenzo Hall, said keeping details secret about a flaw affecting millions of iPhone users “is exactly opposite the disclosure practices of the security research community. The FBI and Apple have a common goal here: to keep people safe and secure. This is the FBI prioritizing an investigation over the interests of hundreds of millions of people worldwide.”

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