"Protect the Data" from the Evil Maid
I recently posted "Protect the Data" from Whom?. I wrote:
[P]rivate citizens (and most organizations who are not nation-state actors) do not have a chance to win against a sufficiently motivated and resourced high-end threat.
Joanna Rutkowska provides a great example of the importance of knowing the adversary in her post Evil Maid goes after TrueCrypt!, a follow-up to her January post Why do I miss Microsoft BitLocker?
Her post describes how she and Alex Tereshkin implemented a physical attack against laptops with TrueCrypt full disk encryption. They implemented the attack (called "Evil Maid") as a bootable USB image that an intruder would use to boot a target laptop. Evil Maid hooks the TrueCrypt function that asks the user for a passphrase on boot, then stores the passphrase for later physical retrieval.
The scenario is this:
- User leaves laptop alone in hotel room.
- Attacker enters room, boots laptop with Evil Maid, and compromises TrueCrypt loader. Attacker leaves.
- User returns to hotel room, boots laptop, enters TrueCrypt passphrase. Game over.
- User leaves laptop alone in hotel room again.
- Attacker enters room again, boots laptop with Evil Maid again, and retrieves passphrase.
Joanna recommends implementing a product that supports Trusted Platform Module (TPM), like Microsoft BitLocker. A detection-oriented workaround is to calculate hashes of selected disk sectors and partitions and decide that mismatches indicate an intrusion has occurred. That approach still misses BIOS-based attacks but it's the best one can do without TPM support.
Comments
I'm not saying that understanding the soft targets within the devices and operating systems we use isn't important. But it's a big world out there and these attack vectors just don't seem very likely to me.
We are better served to fill the gaping holes before we worry about evil maids.
Mike Rothman
http://blog.securityincite.com
http://blog.eiqnetworks.com
I haven't used TC's full disk encryption yet. Does it support key files the same way as it does for encrypted volumes?
-oldami
Also, such a party doesn't want the victim to know that the victim has lost his data.
I understand the point, that Truecrypt lacks the appropriate protections against tampering of a host machine to protect the encrypted data. 0 trust in protecting your data means you might want to consider another product or method. My point is that if they did implement the checks suggested, there are still ways to get that password.
This just cannot end well :-(