A pile of dead Apple laptop batteries, victims of Charlie Miller's research.
Updated below to clarify Barnaby Jack’s prior research.
Your laptop’s battery is smarter than it looks. And if a hacker like security researcher Charlie Miller gets his digital hands on it, it could become more evil than it appears, too.
At the Black Hat security conference in August, Miller plans to expose and provide a fix for a new breed of attack on Apple laptops that takes advantage of a little-studied weak point in their security: the chips that control their batteries.
Modern laptop batteries contain a microcontroller that monitors the power level of the unit, allowing the operating system and the charger to check on the battery’s charge and respond accordingly. That embedded chip means the lithium ion batteries can know when to stop charging even when the computer is powered off, and can regulate their own heat for safety purposes.
When Miller examined those batteries in several Macbooks, Macbook Pros and Macbook Airs, however, he found a disturbing vulnerability. The batteries’ chips are shipped with default passwords, such that anyone who discovers that password and learns to control the chips’ firmware can potentially hijack them to do anything the hacker wants. That includes permanently ruining batteries at will, and may enable nastier tricks like implanting them with hidden malware that infects the computer no matter how many times software is reinstalled or even potentially causing the batteries to heat up, catch fire or explode. “These batteries just aren’t designed with the idea that people will mess with them,” Miller says. “What I’m showing is that it’s possible to use them to do something really bad.”
Miller discovered the two passwords used to access and alter Apple batteries by pulling apart and analyzing a 2009 software update that Apple instituted to fix a problem with Macbook batteries. Using those keys, he was soon able to reverse engineer the chip’s firmware and cause it to give whatever readings he wanted to the operating system and charger, or even rewrite the firmware completely to do his bidding.
From there, zapping the battery such that it’s no longer recognized by the computer becomes trivial: In fact, Miller permanently “bricked” seven batteries just in the course of his tinkering. (They cost about $130 to replace.) More interesting from a criminal perspective, he suggests, might be installing persistent malware on the chip that infects the rest of the computer to steal data, control its functions, or cause it to crash. Few IT administrators would think to check a battery’s firmware for the source of that infection, and if undiscovered the chip could re-infect the computer again and again.
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