<A href="http://www.theregister.co.uk/2011/11/17/malware_milks_cloud/" target="_blank">You can install a program on your computer letting legitimate firms take advantage</A> of your unused computing cycles. Or. You can (mistakenly) install Trojan-Downloader.Win32.MQL5Miner.a and the malware writers will collect money from a, possibly legitimate, firm to use your computer without your knowledge.