In the world of rootkits we already see very effective polymorphism, but we have yet to make public the functions of the more powerful rootkits like Storm, which even change their packing code every 10 minutes or so.
"...the Storm cluster has the equivalent of 1-10M (approximately) 2.8 GHz P4s with 1-10 petabytes of RAM (BlueGene/L has a paltry 32 terabytes). In fact this composite system has better hardware resources than what's listed at http://www.top500.org for the entire world's top 10 supercomputers.." - Peter Gutmann, 2007
Well that's great, considering if it's still around, and has not been sold off piece by piece, like researchers say it has, it would be quite larger than 1-10 petabytes total RAM. It would far outperform all 10 of the most powerful supercomputers combined.
Can you imagine the power of such a large zombie network, not even in terms of blackhat use but computational power? Holy fuck.