Have you tried (and failed) to remove those annoying pop-ups known as adware? There may be reason. You can manually remove adware components one by one, but there is a good chance you would miss some of them. Adware and other types of spyware often install in unusual places to make it as difficult as possible to uninstall.

The United States Computer Emergency Readiness Team (US-CERT) recommends running a legitimate product specifically designed to remove spyware. Many products now offer free downloads and trials.

Adware is considered a form of spyware, and can monitor and profile your web usage, send you pop-up ads, and redirect your browser to specific web sites. Adware can be installed without the user's knowledge, and adware components typically install alongside a shareware or freeware application. While adware is not as dangerous as other infections, it can be incredibly annoying and invasive.

According to US-CERT the following symptoms may indicate that spyware is installed on your computer:

* You are subject to endless pop-up windows

* You are redirected to web sites other than the one you typed into your browser

* New, unexpected toolbars appear in your web browser

* New, unexpected icons appear in the task tray at the bottom of your screen

* Your browser's home page suddenly changed

* The search engine your browser opens when you click "search" has been changed

* Certain keys fail to work in your browser (e.g., the tab key doesn't work when you are moving to the next field within a form)

* Random Windows error messages begin to appear

* Your computer suddenly seems very slow when opening programs or processing tasks (saving files, etc.)

Because of the extra processing, spyware may cause your computer to become slow or sluggish. There are also privacy implications:

* What information is being gathered?

* Who is receiving it?

* How is it being used?

How can you prevent spyware from installing on your computer?

To avoid unintentionally installing it yourself, follow these good security practices:

* Don't click on links within pop-up windows - Because pop-up windows are often a product of spyware, clicking on the window may install spyware software on your computer. To close the pop-up window, click on the "X" icon in the titlebar instead of a "close" link within the window.

* Choose "no" when asked unexpected questions - Be wary of unexpected dialog boxes asking whether you want to run a particular program or perform another type of task. Always select "no" or "cancel," or close the dialog box by clicking the "X" icon in the titlebar.

* Be wary of free downloadable software - There are many sites that offer customized toolbars or other features that appeal to users. Don't download programs from sites you don't trust, and realize that you may be exposing your computer to spyware by downloading some of these programs.

* Don't follow email links claiming to offer anti-spyware software - Like email viruses, the links may serve the opposite purpose and actually install the spyware it claims to be eliminating.

As an additional good security practice, especially if you are concerned that you might have spyware on your machine and want to minimize the impact, consider taking the following action:

* Adjust your browser preferences to limit pop-up windows and cookies - Pop-up windows are often generated by some kind of scripting or active content. Adjusting the settings within your browser to reduce or prevent scripting or active content may reduce the number of pop-up windows that appear. Some browsers offer a specific option to block or limit pop-up windows. Certain types of cookies are sometimes considered spyware because they reveal what web pages you have visited.

Whether you like it or not, spyware and adware are here to stay. A good monitoring and removal tool can be a useful asset in your fight against these invasive technologies.