If your computer is behaving strangely, more than likely it is caused by a virus of some type. This is especially true if your computer is working fine one day and then all of a sudden decides to act up after you have clicked on something unusual. Viruses can be found in e-mails, on websites, and even on social networking pages. They can cause systems to crash, the Internet not to work properly, or the computer to give you weird pop-ups. Even worse, they can make you vulnerable to people who want to steal information from you. The best way to ensure that these things don’t happen to you is to keep protected with antivirus firewall software.