Another part of the Windows web browsing experience us Linux users miss out on:
Malignant toolbar installs itself into Internet Exploiter, redirects home page/web searches to xupiter.com (owned by a shadowy Hungarian company, apparently) or the sites of businesses who paid them for placement (and who are, I would guess, unlikely to be highly ethical), and downloads pop-up gambling games behind your back. The toolbar resists attempts at uninstallation, and the programmers keep changing its code to keep one step ahead of anti-spyware tools.
Healan said some installations probably occurred when people clicked "OK" in a pop-up box without really knowing what they had agreed to, or when they meant to close the pop-up window.