The convoluted case of a recent malware-spam campaign serves as an illustrative example of the riduclous, Rube Goldberg-esque lengths criminals will go to control your computer.
It all starts with a spam email that purports to originate with a Bitcoin management service I had previously never heard of, called OK Pay. Clearly the message didn't originate with this service, but it claimed that Your BitCoin wallet has been successfully completed. Setting aside the message creator's obvious inability to logically parse words in a written language, the spam essentially says that I've received 154.1523 bitcoins on some wallet, somewhere.
At today's exchange rate, that converts to somewhere north of $43,000 -- a not-insignificant sum. Who wouldn't want to click a link that's labeled "Download the wallet" embedded in the message? I imagine some message recipients -- who would, naturally, laugh off an offer to split 2.8 gajillion United States Dollars from an African government official -- thinking to themselves, "Bank error in my favor!"