  In the last years, cryptocurrencies are increasingly popular. Even people who
are not experts have started to invest in these securities and nowadays
cryptocurrency exchanges process transactions for over 100 billion US dollars
per month. However, many cryptocurrencies have low liquidity and therefore they
are highly prone to market manipulation schemes. In this paper, we perform an
in-depth analysis of pump and dump schemes organized by communities over the
Internet. We observe how these communities are organized and how they carry out
the fraud. Then, we report on two case studies related to pump and dump groups.
Lastly, we introduce an approach to detect the fraud in real time that
outperforms the current state of the art, so to help investors stay out of the
market when a pump and dump scheme is in action.
