I have been hearing this word the whole day long. Can any one give me a brief intro? How does it differ from ASLR?
HiASLR is a term that represents the improved ASLR in Windows 8. The "hi" part refers to the improvement in entropy generated by the increased number of random bits that the stack and heap can be offset by. Microsoft also included randomisation to various system heaps, system tables, etc. to make the possibility of using a NOP sled or information leak more difficult.
The following table is taken from Ken Johnson and Matt Miller's "Exploit Mitigation Improvements in Win8" talk at BlackHat USA 2012.
Note that the final column represents High Entropy, which is the official name for HiASLR.