Millions of web surfers are being targeted by a single malvertising group. Hackers have compromised more than 120 ad servers over the past year in an ongoing campaign that displays malicious advertisements on tens of millions, if not hundreds of millions, of devices as they visit sites that, by all outward appearances, are benign.

https://blog.confiant.com/tag-barnakle-one-year-later-120-more-revive-adserver-hacks-f3e5b3bc8e70