My approach to this is largely empirical, and using a variety of platforms to analyse and curate follower sources. However, a few people have recently asked me if there’s some automatic way to detect accounts that have (a large proportion) of fake followers. This require assigning some sort of trust score based on multiple criteria, such as this tool for Twitter:
Has anyone developed a proprietary tool? Or does anyone have access to one?
How should the tool check the fakeness of the account?
Amount of followings or engagement?
I guess that this tool is not really needed. But may be it exists.
Here is a tool by mpsocial user @hvp17 that can help you identify Instagram Accounts that are botting, doing F/U. Its still in develpoment but it works for up to 100-200 accounts at a time.