  Recent evidence has emerged linking coordinated campaigns by state-sponsored
actors to manipulate public opinion on the Web. Campaigns revolving around
major political events are enacted via mission-focused "trolls." While trolls
are involved in spreading disinformation on social media, there is little
understanding of how they operate, what type of content they disseminate, how
their strategies evolve over time, and how they influence the Web's information
ecosystem. In this paper, we begin to address this gap by analyzing 10M posts
by 5.5K Twitter and Reddit users identified as Russian and Iranian
state-sponsored trolls. We compare the behavior of each group of
state-sponsored trolls with a focus on how their strategies change over time,
the different campaigns they embark on, and differences between the trolls
operated by Russia and Iran. Among other things, we find: 1) that Russian
trolls were pro-Trump while Iranian trolls were anti-Trump; 2) evidence that
campaigns undertaken by such actors are influenced by real-world events; and 3)
that the behavior of such actors is not consistent over time, hence automated
detection is not a straightforward task. Using the Hawkes Processes statistical
model, we quantify the influence these accounts have on pushing URLs on four
social platforms: Twitter, Reddit, 4chan's Politically Incorrect board (/pol/),
and Gab. In general, Russian trolls were more influential and efficient in
pushing URLs to all the other platforms with the exception of /pol/ where
Iranians were more influential. Finally, we release our data and source code to
ensure the reproducibility of our results and to encourage other researchers to
work on understanding other emerging kinds of state-sponsored troll accounts on
Twitter.
