Two meanings:
An organisation which employs ‘internet trolls’ to make posts on various topics, marketing and politics on the Internet. The most notorious troll farm is the St. Petersburg-based Internet Research Agency, which made extensive efforts to manipulate the 2016 US Presidential election, is alleged to have had a role in manipulating opinion in the 2016 UK Brexit referendum and in other Western European elections.
Alternately a ‘Turkey Farm‘ with whose managers and staff are unpleasant as well as incompetent.