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July 27, 2011

Grabbing OSX Passwords Through FireWire

There was a lot of attention given to yesterday’s news of Passware Kit Forensic v11 being able to extract your Lion login password if your computer was locked or sleeping, even with FileVault turned on. It’s worth pointing out that not only is this old news (from 2006), it isn’t even a vulnerability specific to Mac OS X, but rather a vulnerability introduced on computers with FireWire (or iLink) ports. The FireWire specification provides external devices with the interesting ability to interact directly with system memory (without going through the OS). While in theory this could open up interesting uses, in reality it just enables vulnerabilies due to the fact that a computer’s live memory can be used to extract data or manipulate parameters. Windows systems are vulnerable to this attack too, and there are tools (eg. winlockpwn) that exist that allow an attacker to unlock a locked Windows machine, or dump its memory, just by plugging into it via FireWire/iLink.

This flaw definitely has security and privacy implications, but only if the attacker is able to get physical access to your computer. As I’ve pointed out on a number of occasions, if someone gets phsysical access to your computer, it’s game over. Even without a FireWire port, techniques such as the Cold Boot Attack may allow an attacker to recover passwords or decryption keys from live memory. Until Apple completely phases out FireWire in favour of Thunderbolt,  this will continue to be an issue to be aware of. Thunderbolt itself, although not fully tested, may yet be found to have some similar issues; although I’m hoping Apple/Intel will have learnt from past mistakes.

There’s not a huge amount you can do to protect yourself apart from:

  1. Disable automatic login, and shut down your computer when you don’t plan on using it (especially if you’re going to be away from it for a while). Note that for this to really be effective, you’ll need to enable FileVault as well – otherwise the attacker will be able to access your unencrypted HD.
  2. Block your FireWire port with epoxy – or destroy it altogether.

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