How the FBI Cracked the iPhone Encryption

An urgent meeting inside FBI headquarters little more than a week ago is what convinced federal law enforcement officials that they may be able to abandon a brewing legal fight with tech giant Apple, sources told ABC News today.

In the days after the December 2015 massacre in San Bernardino, California, which killed 14 people and wounded 22 others, the iPhone left behind by one of the shooters, Syed Farook, was secretly flown to the FBI's laboratory in Quantico, Virginia, sources said.

The FBI had been unable to review the phone's contents due to a security feature that -- after 10 failed attempts to enter the 4-digit access code -- would render the phone's files forever inaccessible.

By last month, the FBI was at an impasse with Apple, which fought a court order telling the company to help authorities bypass the security feature. Apple maintained the U.S. government was asking it to create a "backdoor" into its devices that would endanger the privacy of hundreds of millions of iPhone users around the world.

"It is in our view the software equivalent of cancer," Apple CEO Tim Cook recently told "World News Tonight" anchor David Muir.

But the FBI insisted it had a responsibility to access any data potentially relevant to the deadly terror attack in San Bernardino.

"I don't know whether there is evidence of the identity of another terrorist on the phone, or nothing at all. But we ought to be fired in the FBI if we didn't pursue that lead," FBI Director James Comey told a House panel in February.

As the legal battle played out, the FBI appealed to cyber experts around the world for help.

"We've talked to anybody who will talk with us about it, and I welcome additional suggestions," Comey said during a House hearing four weeks ago.

In response, countless companies and hackers -- including what one source familiar with matter called many "whackadoodles" -- came forward claiming to have a way into Farook's phone, sources said.

But nothing appeared viable. That is, until a company that the FBI has yet to identify came forward about two weeks ago. After initial contacts with the FBI, company officials flew to Washington to lay out their solution, sources told ABC News.

On Sunday, March 20, in a meeting at FBI headquarters, company officials demonstrated their technology on another iPhone. Convinced it would work, the FBI greenlighted applying it to Farook's phone, sources said.

This past weekend -- just days ago -- the attempt was made, and "the FBI has now successfully retrieved the data stored on" the phone, according to the Justice Department.

Forensic examiners are now attempting to exploit potential evidence from the phone. It's unclear if anything of investigative value has been found yet.

The FBI has refused to identify the company that offered the solution, with one source citing a "mutual agreement." Nevertheless, Apple did not play a part in finding the solution, company officials said.

As for whether the solution might be shared with Apple, it's a decision that will be made through consultation with multiple federal agencies, sources said.

One federal law enforcement source said it's important to emphasize that the ultimate solution identified in this case was not found despite the lawsuit filed against Apple, but because of it.

The solution was "generated as a result of the media attention," the source said.

At the same time, the source said federal authorities believe the end to the current litigation should not end the national discussion about balancing the interests of security and privacy.

"Our need for public safety and our need for privacy are crashing into each other, and we have to sort that out as a people," Comey said recently. "This world some people imagine where nobody can look at your stuff is a world that will have public safety costs."