Malicious Actors on Twitter: A Guide for Public Health Researchers.

Social bots and other malicious actors have a significant presence on Twitter. It is increasingly clear that some of their activities can have a negative impact on public health. This guide provides an overview of the types of malicious actors currently active on Twitter by highlighting the characteristic behaviors and strategies employed. It covers both automated accounts (including traditional spambots, social spambots, content polluters, and fake followers) and human users (primarily trolls). It also addresses the unique threat of state-sponsored trolls. We utilize examples from our own research on vaccination to illustrate. The diversity of malicious actors and their multifarious goals adds complexity to research efforts that use Twitter. Bots are now part of the social media landscape, and although it may not be possible to stop their influence, it is vital that public health researchers and practitioners recognize the potential harms and develop strategies to address bot- and troll-driven messages.