What viruses and spyware have in common is that they are maliciously coded programs that plague almost every person who uses the Internet.
The difference between the two however is that a virus can spread from computer to computer, spyware plants itself within your system.
They both cause damage in their own unique ways.
Because viruses can spread from system to system they can damage very large computer networks.
They commonly spread through e-mail attachments and files which are shared between users.
They can slow down your computer and use mail programs within your system to replicate themselves so they can spread on to other computer systems.
While spyware may not damage your system it can be just as dangerous.
It is planted within your system with the purpose of stealing your information.
You can accidentally put it on your computer when you download free software or by visiting a website that is not trustworthy.
Spyware can be hard to remove as it can replicate itself and hide very deep within your system and within your program files.
Another form of spyware is called adware.
It is created to monitor your web usage.
Like spyware it can be installed along with other forms of software which you are downloading.
A common mistake people make is not reading the end - user agreement and click on "Agree" without acknowledging what they are actually accepting.
Adware can also be included in what look like genuine anti-spyware programs.
Adware has the main purpose of tracking your Internet usage and deliver pop-up adverts that are related to your browsing history.
It can forward you browser address to different pages, even if you have no intention of accessing these other pages.
This can be very serious as it may track your keystrokes and record passwords and credit card details.
However adware usually is not a security threat.
It is advisable to use more than one anti-spyware program on your system.
New types of spyware are created daily and one program may not be effective in keeping your computer clean.
Two of the most popular anti-spyware programs are "Adaware" and "Spybot".
There are some programs available that will scan your system for spyware and report back but will not correct the errors.
They will request that you sign up and pay to have the spyware removed - this can get very expensive very quickly.
It's important to be careful with the anti-spyware programs that you install.
Some have their own spyware built in and delete any other spyware programs that they find.
Some will try to create a false sense of fear in you by saying that your computer is infected.
This can happen when you may only have advertising cookies that are easily removed.