26. October 2009 · Comments Off on Evil Maid attack shows that laptop hard drive encryption not the silver bullet · Categories: Breaches, Malware, Risk Management · Tags: , , , ,

As important as laptop hard drive encryption is, it's not the silver bullet for protecting confidential data on laptops. Bruce Schneier described Joanna Rutkowska's "evil maid" attack against a disk encryption product. This type of attack would probably work against any disk encryption product because disk encryption does not defend against an attack where the attacker gets access to your encryption key.

As usual, risk management is about understanding the threat which you are trying to mitigate. Disk encryption does solve the stolen laptop problem. But if an attacker can get access to your laptop multiple times without your realizing it, the evil maid attack can defeat disk encryption.

PGP, a disk encryption vendor, discusses the limitations of disk encryption and as well as other defenses available to protect against evil maid and other attacks.

Bruce Schneier notes that two-factor authentication will defeat the evil maid attack. BTW, don't leave your token in the hotel room for the evil maid to find. 🙂

Last week at Black Hat, Peter Kleissner, a young software developer from Vienna,
Austria, showed an interesting variation on a rootkit he
calls Stoned which he said can bypass disk encryption. However, I don’t think any disk encryption product, by itself, claims that it cannot be
bypassed by a keylogger.

Here is the scenario: If you lose your PC and the disk
is encrypted with a quality disk encryption product, you can have a high degree
of confidence that no encrypted information will be disclosed.

However, if the
PC is returned to you, you cannot be sure that a root kit and a keylogger have
not been installed on the machine. The risk of disclosing information occurs
when you boot up the machine and authenticate. At that point the keylogger can
capture your credentials and eventually access all the data on the disk (as you

Also, the risk of your PC being “rootkitted” (if there is such a word) while browsing increases if you are working on your PC as an Administrator. Clearly
organizations have policies against this and are able to enforce it.