botnet doesnt have cpu to 100 % ----- with minerd just use -t x and u set threads ... so cpu stays low ....

im using on the servers im administrating  3 threads on xeon e3 1245 v2 (8 threads max) ----- im using only 36 % of each cpu and only 25  of my rack ( so half rack )

that brings me to 40 - 50 khash / sec

that dude with 1 mhs  has either a bot net or he is administrating something like  1 or two full rack of high end servers ....