Viruses have always been a major problem for computers, but now they are changing into something that might make them a bigger problem than ever before. Traditionally viruses have been limited, either to an operating system or to a specific web browser. That might no longer be the case moving forward. A new type of virus has been developed that can infect multiple operating systems and browsers. Bit9 has a very detailed post about this virus, I would highly advise reading it.