Norton.com/Setup - Stats demonstrate that there are around 55,000 computer viruses in existence and a new is coming up every 18 seconds. A virus can do things from erasing system files, showing ads to stealing your credit card and personal information. Most computer users get infected by downloading pirated software, or an email attachment or any other kind of software with a virus attached to it. There are a number of facts that an individual should be aware of, but eventually, getting anti-virus software installed is an absolute necessity. Firstly, you must not open any attachment sent by an individual that you do not know or you feel suspicious about the attachment. That is how most of the computers get infected.