This means, if you leave your system in either "sleep" or "hibernate" mode, it has been proven that the keys used to encrypt and decrypt files or an entire drive can be found -- still resident in memory -- and used to access private data at will.
Also troubling is that the researchers warn that this attack could be used to snoop on SSL sessions (how Web site communication is commonly secured in transit to and from your PC) as well as DRM technologies (such as is used for eBooks and music files).
It's important to note that it's not the encryption scheme, which is the mathematical algorithm used to scramble legible information into gibberish, that has been proven vulnerable. It's how all data is stored in RAM that creates the condition. And by using software to scan RAM for private encryption keys, after either booting from across a network, external, or USB drive, the secret keys can be uncovered, for a short period of time, after the machine has been turned off.
A system still getting power, such as in hibernate mode, is vulnerable to this attack.
What all of this means is that walking away from your system in an office, hotel room, or any place you don't feel secure: relying on the system's automatic screen saver password, or going into sleep mode isn't safe enough. You have to turn the system off, and if you're really concerned, wait a few minutes until the RAM has no more power. What's more, the researchers found, is that the length of time that residual files remain available in RAM memory, including crypto keys, can be extended through the use of giving DRAM modules a cold blast of compressed air.
None of this is going to change my behavior much. I'm still going to continue using TrueCrypt. Only I'll now shut my system off when leaving it unattended in a hotel room, or other place I don't feel secure. And I'll keep an eye out for strangers rapidly approaching me armed with little more than a can of GasDuster.