For those of you who think that surfing the web and not downloading anything still ensures that your machine will not be infected by a virus/malware, here is the truth.
As the article points out  (once again) malware is distributed through online advertisements placed on sites. It is installed without any user interaction required. This is not a connection that can be blocked with a firewall. These programs take advantage of problems that exist on the application, being application specific. Therefore it is important in choosing and keeping our internet connected applications up to date.
 Matt Chapman, vnunet.com, "Ad-based Trojan hits MySpace, Bebo and others" – http://www.vnunet.com/vnunet/news/2198466/advert-trojan-dogs-myspace-bebo