Cold Boot Attacks on Encryption Keys

Abstract : Contrary to popular assumption, DRAMs used in most modern computers retain their contents for seconds to minutes after power is lost, even at operating temperatures and even if removed from a motherboard. Although DRAMs become less reliable when they are not refreshed, they are not immediately erased, and their contents persist sufficiently for malicious (or forensic) acquisition of usable full-system memory images.

These guys have come up with a new and interesting type of attack to recover the encryption keys from the DRAM.
http://citp.princeton.edu/memory/