There are brilliant computer programmers out there who spend all of their time looking at internet connections and trying to find someone who has an open port so that they can hack into that computer. Everyone connects to the internet through a port to your internet provider. If your connection, or port, is unprotected then criminals can get in and do damage and steal information from your computer. They can do it without you even knowing until it is too late. They can get into your computer and leave a piece of software that will send them regular reports of where you visit on the internet so they can send you pop up ads for products they think you will buy. These guys break into your computer, leave a harmful virus on your computer, steal your personal information, and then think you will buy products from pop up ads that will cause your computer to not function properly at all. Maybe they are not as smart as they appear to be.
The way to stop internet prowlers is with firewalls and anti-virus software. Windows XP has an internet firewall built into it and all you need to do is turn it on and you are protected. A quality anti-virus software like Norton Anti-Virus can not only scan incoming traffic for you but it also has a firewall that can help the Windows firewall protect your computer from criminals. Many other quality anti-virus software is also available to help you protect your PC as well. Never connect to the internet with a firewall and anti-virus software.
The other way criminals hack into your computer is when you let them in. If you receive an email from someone you don’t know and either click on a link in that email or download the attachment to that email then you just invited a virus. Firewalls can’t help you when you download an attachment from an email so never download an attachment from someone you do not know. Never download a file from an internet site you are not sure of. The quickest way to get a virus on your computer that you cannot get rid of is to download a suspect piece of software from the internet. If your firewall and your anti-virus software is on then they can help you most of the time but always be very careful with what you download on to your computer.