Apple is reportedly working to make iPhone security almost impenetrable, so tight that even it cannot gain access to a locked device.

Word of the lockdown comes from The New York Times, which cites "people close to the company and security experts" as its sources.

Making the iPhone unhackable involves closing up the loophole at the center of Apple's security dispute with the FBI concerning California gunman Syed Rizwan Farook's handset.

The government agency wants Apple to build software that would allow it to circumvent the passcode for the ISIS devotee's handset, a hacking method that only works because iPhone software can be updated even when a device is locked.

By closing this long-standing vulnerability—which exists as a troubleshooting measure to help fix faulty devices—a locked iPhone would be impenetrable, even to Apple itself.

Apple has reportedly been working on closing the loophole for some time, but now seems like a good time to prioritize a fix. Company CEO Tim Cook has vowed to fight the court order obtained by the FBI, insisting that granting the government agency backdoor access to iOS could set a "dangerous precedent".

Apple has until Friday, February 26 to formally challenge the court order.