The fungibility of trolls makes it possible for trolls to embed themselves anywhere.
Social media are particularly vulnerable and extremely easy to access.
In fact almost all active social media users reading this right now have likely done some form of conscious and inadvertent trolling.
From Wikipedia: A Troll is a person who sows discord on the Internet by starting arguments or upsetting people, by posting inflammatory, extraneous, or off-topic messages in an online community (such as a newsgroup, forum, chat room, or blog) with the intent of provoking readers into an emotional response or of otherwise disrupting normal, on-topic discussion, often for the troll's amusement.
What is extremely important to understand is that trolling isn't all bad.
Constructive conflict, cognitive dissonance, debates, arguments and controversy cause human beings to think more and in doing so they learn more in the process.
That is one of the problems I have with the moderation policies of various social media outlets.
Moderation is a form of suppression and censorship when it is subjectively applied.
In fact Russian and Trump trolls could be working right now within such social media as Facebook, Twitter, Quora, Newsvine, LinkedIn etc etc ETC!