

To protect yourself from serious malware infection, you must be extraordinarily careful about how you close a pop-up window. Even if your browser is set to block pop-ups you're still going to get some because no pop-up blocker is perfect. Most are merely annoying but a significant number- such as the "Antivirus 2009" pop-up described below-are designed to infect your computer with spyware that makes your computer unusable.

When you browse the web with a Windows computer you're sometimes presented with pop-up windows-and "pop-under" windows that you don't notice until you close your main browser window.
