Ask HN: How do publishers deal with bad ads?

Its hard to find resources on how large content publishers who use network ads deal with bad ads. Why have I never heard of a company that they can outsource bad ad reporting to? Moreover, is there liturature on how different publishers approach this issue? How prevelent is it? Whats a good industry estimation of the proportion of users exposed to bad ads report them? How can that ratio be improved? Are there any case studies worth looking at? How proactive are publishers at stopping bad ads?

Looking into this, I can't help but be surprised at how little information is publicly available and how unexhaustive that informatino is.

Does anyone have any good resources on the topic, or have any insight into questions like these?