Best way to know if job post is a ghost post is to monitor the board for a few weeks, months then see how many of the same posts repeat themselves. That's how I verified jobs posted on LinkedIn and Indeed. LinkedIn jobs are easy to tell, as they have a number of people applied attached to the post. Indeed.com ads tend repeat often, some day after day or week after week. I would say what is needed an application that looks at these boards, daily, and indexes the job posts, keeping track the frequency of these job posts.