[Buge]

I'm surprised that it was large instances instead of GPU instances. GPU would be much more profitable if you are mining a scrypt coin (or sha256 coin but that would be stupid because of ASICs).

Maybe it was some other type of coin (I'm not sure if primecoin is more CPU-friendly).

[bwood]

Note that the author is only assuming that bitcoin/altcoin mining was the intended goal of the attack.