Got warning from ad network, fake boosted impressions/conversions.

Hi, guys yesterday received warning from ad network. Working with them from 2014 years, never had any problems.

I did not done this, so this seems that someone is doing from my competitors, or angry user. So my question is
or somebody had like this situation? What I can do to prevent like this situation?

Throw it away, clean it (traffic) and ask your network for assistance and possible solution. If you are serious and never had such issues earlier i think that you will be fine.

Send them a polite and detailed e-mail containing proof of your traffic - whether this is your blog's Google Analytics, screenshots from your autoresponder or PPC ad campaigns. Do emphasize that you've been a partner since 2014 and would not do such a thing. I hope you resolve your problem, best of luck.