  Growing evidence points to recurring influence campaigns on social media,
often sponsored by state actors aiming to manipulate public opinion on
sensitive political topics. Typically, campaigns are performed through
instrumented accounts, known as troll accounts; despite their prominence,
however, little work has been done to detect these accounts in the wild. In
this paper, we present TROLLMAGNIFIER, a detection system for troll accounts.
Our key observation, based on analysis of known Russian-sponsored troll
accounts identified by Reddit, is that they show loose coordination, often
interacting with each other to further specific narratives. Therefore, troll
accounts controlled by the same actor often show similarities that can be
leveraged for detection. TROLLMAGNIFIER learns the typical behavior of known
troll accounts and identifies more that behave similarly. We train
TROLLMAGNIFIER on a set of 335 known troll accounts and run it on a large
dataset of Reddit accounts. Our system identifies 1,248 potential troll
accounts; we then provide a multi-faceted analysis to corroborate the
correctness of our classification. In particular, 66% of the detected accounts
show signs of being instrumented by malicious actors (e.g., they were created
on the same exact day as a known troll, they have since been suspended by
Reddit, etc.). They also discuss similar topics as the known troll accounts and
exhibit temporal synchronization in their activity. Overall, we show that using
TROLLMAGNIFIER, one can grow the initial knowledge of potential trolls provided
by Reddit by over 300%.
