I've looked into GPU mining bitcoins before, but it seems like startup costs to actually make more off bitcoins than it costs per kilowatt hour to run the rig is growing. A botnet's not going to be anywhere near as efficient given that CPU's aren't nearly as good at mining and especially if you want the thing to be stealthy. However, it's pretty obvious from the screencap of task manager in the link that whoever designed this certainly wasn't going the stealthy route since it's maxing out the CPU.
On a sidenote, I wouldn't be surprised if there was governmental involvement. The media's been slinging the bitcoin rhetoric pretty hard the past few weeks playing the forthcoming regulations card, and if the US or EU wanted to start debasing bitcoins, now would be an opportune time to do it.