As with the computer virus, spyware can be broken down into a number of different categories. Most users are familiar with the term 'adware' which refers to software which serves annoying ads. There are however a number of other spyware variants you should be aware of.

To begin with it is important to have a clear definition of spyware. This will also help us understand why the term is commonly used to encompass a number of different variants. Spyware is a program, usually installed without your knowledge, which records what you do on your computer and then shares it with its creator.

The information which the spyware program collects can vary from the websites you visit to log-in and passwords for your online banking site. The sharing of your personal information with a third party is why spyware in its purest form is labelled as a malicious threat and clearly is a major privacy issue.

Adware is the second mostly commonly used term. Adware is designed to display adverts relevant you, commonly based on your surfing habits, to generate Pay-Per-Click advertising revenue or sales through affiliate links. Adware is commonly bundled with free software by developers instead of charging a price.

The malicious nature of adware can vary enormously. At one of the scale, adverts are displayed in a non-intrusive manner in a window within the free program you have downloaded. When the program is not running, ads are not displayed. At the other end of the scale, a user could find their desktop overwhelmed as the adware program spews out multiple pop up ads in a very aggressive manner. Whilst it may be possible to believe the former is not transmitting personal data to a third party, it is difficult to expect the later not to.

The adware issue is further complicated by marketing companies who do not like their software being labelled 'spyware.' These marketing companies generate millions of dollars of income often via recognised brand name clients. So to avoid legal issue security companies refer to this software as PUPs (potentially unwanted programs).

Browser hijackers are another aggressive form of spyware. They attack important browser settings like your default homepage which your browser loads when you start the program. Hackers direct you to sites which generate revenue for them like the Russian website 'Cool Web Search'. Browser hijackers can also insert sites into your bookmarks. They also can cause your browser to crash and stop working completely and are typically difficult to remove.

Key Loggers capture all your key strokes into a DLL file which the creator retrieves. Software key loggers are often bundled with a Trojan Virus which gives the creator access to your computer.

Here are some tips and strategies to fight the different types of spyware.
- Keep Windows XP and ALL your web browsers (including Internet Explorer and FireFox) up to date with the latest patches.
- Install a reputable anti-spyware program like Webroot Spy Sweeper or PC Tools Spyware Doctor. Run frequent scans and keep the definitions up to date.
- Install a reputable anti-virus program like Norton Anti-Virus or McAfee VirusScan. Run frequent scans and keep the definitions up to date.
- Install a firewall which manages both inbound and outbound connections. Top personal firewall software picks include Zone Labs's Zone Alarm and Norton Personal Firewall. Alternatively purchase a router with a hardware firewall.
- Avoid downloading free software programs including screensavers and weather toolbars.
- Avoid know high spyware risk area on the internet including illegal music sharing sites, Peer-to-Peer programs, free game download sites and adult sites.