Adware can do a number of things from profile your online surfing and spending habits to popping up annoying ad windows as you surf.
In some cases Adware has been bundled (i.e. peer-to-peer file swapping products) with other software with or without the user's knowledge or slipped in the fine print of a EULA (End User License Agreement).
Not all Adware is bad, but often users are annoyed by adware's intrusive behavior. Keep in mind that by removing Adware sometimes the program it came bundled with for free may stop functioning. Some Adware applications act soley as data miners (like Alexa or ComScore) may not perform any activity other than to profile a user?s surfing activity for study.
AdWare can be obnoxious in that historically it has been distributed "drive-by downloads" or uses browser security holes for distribution. Drive-by downloads are accomplished by providing a misleading dialogue box or other methods of stealth installation.
Many times users have no idea they have installed the application. we see this scenrio frequently when a teenager has downloaded a plethora of adware without the parent's knowledge. Some Adware makers make their application difficult to uninstall. Some even deploy counter-attacks in an attempt to thwart their adware being identified and removed or using a resucitator file to prompt the user to re-install even after removal.
A "EULA" or End User License Agreement is the agreement you accept when you click "OK" or "Continue" when you are installing software.
Many users never bother to read the EULA. See http://www.spywareguide.com/analyze/index.php
It is imperative read this agreement before you install any software. No matter how tedious the EULA, you should be able to find out the intent BEFORE you install the software. If you have questions about the EULA- e-mail the company and ask them for clarification. If they cannot clarify this do not install the software.
It is also good practice and download the EULA for safe and legal backup.