A firewall is your gateway and protector against harm
PC Firewalls are the gatekeepers of the computer from web pages and possible programs that will try to invade the space that is in your computer. The most common is thought to be the E-Mail, yet this is not the case. The most common is a virus that is embedded within a web page.
The reason that the web page is such a dangerous means of getting viruses is that all programmers of the Virtual Age know that these pages are easy to get into a computer. When a page is accessed the page is downloaded into two separate locations of the computer. This includes all the pictures and much of the background code. This is a method that is used by many operating systems to help reload pages that much faster when a person is going to them often. The drawback is that when these pages are downloaded and their respective information, so are the viruses that are living on these pages. This means that the person could have just loaded a virus on their computer multiple times without even knowing it.
A good firewall can prevent this as it is checking the information that as it is come to the computer. If there are any bits of code or information that seems suspicious, the firewall will either prevent it from being loaded or will ask if the person is sure that they want to load that page. Some of the best firewall programs have even found viruses that have been slipped into common pages. This is a serious concern to many as the viruses are become more sophisticated with what they can do and the level of damage that can come with these viruses.
A hybrid of the virus is spyware. These are programs that are designed to give information of the computer, the user, and even where the person goes to a secure location. Some viruses also offer this as well, and this is one of the motivations that some have with not doing Internet sales transactions.
Typically three kinds of viruses and each of these are designed for a unique purpose. The worm is the intrusion virus that is designed to get into the system, install background applications, and even copy information to send to another location. The Trojan is a utility-based virus that is used to cripple a system or lock the user out. The third is a broad spectrum of viruses that are usually labeled as just viruses, but are the meat and potatoes of the damage that can be brought upon a person that is unwilling to have a firewall and gamble with the computer.