Check out Wikipedia page about Rainbow table, more specifically the section about how to defeat the effectiveness of these kind of attacks ( http://en.wikipedia

Check out Wikipedia page about Rainbow table, more specifically the section about how to defeat the effectiveness of these kind of attacks ( http://en.wikipedia.org/wiki/Rainbow_table#Defense_against_rainbow_tables http://en.wikipedia.org/wiki/Rainbow_table#Defense_against_r... ) There are 2 examples there which should give you a clear idea what your parent post was referring to.