Communications of the ACM

Recent media attention to spyware [2, 5, 7, 8] has brought to light the blunt intrusion into individual privacy and the uncertain hidden cost of free access to Internet sites, along with freeware and shareware. Most spyware programs belong to the more benign category of adware that delivers targeted pop-up ads based on a user's Web surfing habits. The more malicious type of spyware tracks each keystroke of the user and sends that information to its proprietors. Such information could be used for legitimate data mining purposes or it could be abused by others for identity theft and financial crimes.