Its a clever one that's for sure, all the more impressive when you find out the entire package weighs in at 20MB.... many times the size of Stuxnet and an order of magnitude bigger than your average virus.
It is quite surprising it went undetected for so long given the volumes of data its been allegedly transferring back to C&C. But then I guess the networks being targeted don't have much in place in the way of egress protection mechanisms.
Should be interesting to see how the AV companies react to this in terms of building new screening mechanisms against this zero-day.