Well, you can check the real or fake exchanger by reading about it here on the forum. If you just let us know which exchanger you are talking about instead of waning them A and B then you will get the thousand reviews in no time here. But if you asking the question in general then there is only one way to know real or fakes of website by reading it on the forum, searching in the service discussion section about it. You can also check for the announcement section as sometimes there will be info regarding it if it was published on the forum earlier. Some ICO's are developing exchangers too so they might just be here.