  The short squeeze of Gamestop (GME) has revealed to the world how retail
investors pooling through social media can severely impact financial markets.
In this paper, we devise an early warning signal to detect suspicious users'
social network activity, which might affect the financial market stability. We
apply our approach to the subreddit r/WallStreetBets, selecting two meme stocks
(GME and AMC) and two non-meme stocks (AAPL and MSFT) as case studies. The
alert system is structured in two stpng; the first one is based on
extraordinary activity on the social network, while the second aims at
identifying whether the movement seeks to coordinate the users to a bulk
action. We run an event study analysis to see the reaction of the financial
markets when the alert system catches social network turmoil. A regression
analysis witnesses the discrepancy between the meme and non-meme stocks in how
the social networks might affect the trend on the financial market.
