A few weeks ago a new version of grsecurity 2.1.9 was released . It is worth to mention about it because one new features affect how Linux physical memory forensic analysis will be performed.
Firstly, all physical memory pages which are freed are overwritten. During freeing page frames, a new PaX feature zeroes out them. It means that it will be impossible to recover content of pages such as memory mapped files from memory images which represent /dev/mem or /proc/kcore. Still, we can use methods of analysis which are based on interpreting internal kernel structures or trying to detect and recover hidden data .
Secondly, swap areas can be encrypted. It means that creating bit-by-bit copy of swap space partition from hard disk which was removed from compromised machine is useless.