It will be almost impossible to filter out scammers from legit projects but there are ways. One is to confirm the identity of the people behind the project. Not all pictures of the CEO or the dev team you see are legit. I have a friend that encountered a project that is actually a scam and they used stolen pictures from other legit projects.
Stolen pictures of using stock images of models to show as team members is a common tactic. Because some bounty lovers go for such projects and know some turn scam they might go to check the website and the owners but some pictures they think that all is good and start their bounty spamming, because they are greedy to get paid and not check the team properly.
Fact is that even established team end up with exit scams. Look at the AMBIT mining ICO. The owner Beka has shutdown the site and now posting Instagram stories leaving investors who invested millions of dollars at nothing but dust in their hands.