Largest online social groups.

Most populated communities (with more than 250 users) in the social bulk, with top influencers listed per group. Top influencers are identified as hubs in the bulk network. As evident from the similarities among top influencers, groups reflect specific ecosystems of the Italian voting event: “Movimento 5 Stelle” (M5S), traditional media (Media), media with massive online presence (Web Media), “Partito Democratico” (PD), “Liberi e Uguali” (LEU), “Forza Italia” (FI), “Lega” and “Fratelli d’Italia” (Lega and FdI), and then the augmented human with all his/her interacting bots (Augmented Human). Bot (augmented) infiltration indicates the percentage of bot users (augmented humans) in each group. Excluding the community corresponding to the augmented human (made for 97.9% of bots), the mean bot infiltration in the bulk network is 29.2% while the mean augmented infiltration is 15.7%. The media groups are richer in bots as expected, since they include news media and online accounts of news papers. Note that users not corresponding to public groups, public entities or individuals with a public political profile (e.g., elected for a specific political party) have been anonymized. Interestingly, the account of User09 has been later suspended by Twitter for violating its policies.