malvertising

This is the practice of inserting malicious code into legitimately placed ads which will pop up on your website. The word is a blend of malware and advertising.  The code can do anything from transferring you to a different page, freezing your page, or introducing spyware into your computer to get your credit card or banking details.  It is insidious because its presence is not felt by the website on which the ads appear and the victim does not need to click on the ad for the malware to be downloaded.  And because advertising by its very nature is designed to reach as many people as possible, the reach of the malvertising is similarly broad.