Hi I think they are a scam and here's a picture to prove it. Same: https://forums.digitalpoint.com/threads/fraud-lovecpm-cpmbullet-ecpm-biz-cpxtraffic.2723681/
I can confirm they are faking traffic for their ads with hidden iframes and one ad code often makes over a 1000 requests wasting users bandwidth and slowing down the site. I asked AppNexus about this but I didn't get any answer, so it looks like they don't care about fraudulent traffic in their system. They have good CPM and they are paying but they will get caught and then they will not be able to pay anymore.
The problem isn't AppNexus. They are the technology provider. The problem is the networks get paid anyways, so its a win win. More volume, more money at the expense of programmatic advertisers. PremiumCPM is one of the networks who use AppNexus and ban fraudulent activity immediately without thinking of the potential revenue to be made or lost. Its unacceptable.