A very large number of people use Online Social Networks daily. Such
platforms thus become attractive targets for agents that seek to gain access to
the attention of large audiences, and influence perceptions or opinions.
Botnets, collections of automated accounts controlled by a single agent, are a
common mechanism for exerting maximum influence. Botnets may be used to better
infiltrate the social graph over time and to create an illusion of community
behavior, amplifying their message and increasing persuasion.
This paper investigates Twitter botnets, their behavior, their interaction
with user communities and their evolution over time. We analyzed a dense crawl
of a subset of Twitter traffic, amounting to nearly all interactions by
Greek-speaking Twitter users for a period of 36 months. We detected over a
million events where seemingly unrelated accounts tweeted nearly identical
content at nearly the same time. We filtered these concurrent content injection
events and detected a set of 1,850 accounts that repeatedly exhibit this
pattern of behavior, suggesting that they are fully or in part controlled and
orchestrated by the same software. We found botnets that appear for brief
intervals and disappear, as well as botnets that evolve and grow, spanning the
duration of our dataset. We analyze statistical differences between bot
accounts and human users, as well as botnet interaction with user communities
and Twitter trending topics