The FBI knows how to hack iPhones, and it may help local police do it

The FBI is refusing to tell Apple or the public how it hacked the iPhone of San Bernardino terrorism suspect Syed Farook. But in a letter to local law enforcement obtained by BuzzFeed, the federal agency signaled that it wasn't going to stop with unlocking a single iPhone.

"We will continue to do everything we can to help you consistent with our legal and policy constraints," wrote Kerry Sleeper, an FBI official responsible for managing the FBI's relationships with other law enforcement agencies.

Those "policy constraints" likely include the FBI's desire to keep the details of how it hacks the iPhones a secret. If the security vulnerability exploited by the FBI were revealed, it could enable Apple to fix the flaw and prevent the FBI from using the method on iPhones in the future.

It might seem messy for the FBI to be exploiting secret security flaws to break into iPhones, but in a lot of ways this is the ideal outcome to the FBI's high-profile showdown with Apple. If the courts had ordered Apple to aid the FBI, governments around the world — including repressive regimes with little respect for human rights — would have demanded that Apple provide them with the same assistance.

Instead, the ability to unlock encrypted iPhones will be closely held. The FBI may not be the only organization with the ability to do so — a few foreign governments will likely devote resources to discovering flaws as well — but iPhones are likely to remain secure against the vast majority of attackers. And because Apple will be beefing up iPhone security over time, these organizations will have to work hard to retain the ability to unlock them.

Of course, by keeping security flaws to itself rather than reporting them to Apple, the FBI is leaving Americans' iPhones open to potential exploitation. Critics have argued that securing smartphones should be a higher priority for the US federal government. But that could leave law enforcement agencies with no practical way to access the smartphones of high-value suspects like Farook.

The big question is what happens if Apple ever succeeds in building a truly bulletproof iPhone encryption system. At that point, the government may once again ask the courts to compel Apple to aid the FBI.