Rather than attempting to trick you into visiting a malicious website, malvertising uses advertising networks to spread these malicious Flash objects and other bits of malicious code to other websites. Attackers upload malicious Flash objects and other bits of malicious code to ad networks, paying the network to distribute them like they're real advertisements. You could visit a newspaper's website and an advertising script on the website would download an ad from the ad network. The malicious advertisement would then attempt to compromise your web browser.

http://www.howtogeek.com/227205/what-is-malvertising-and-how-do-you-protect-yourself/