Found here: https://www.schneier.com/blog/archives/2017/02/a_survey_of_pro.html

…in Russia, it’s about flooding the channel with a mix of lies and truth, crowding out other stories; in China, it’s about suffocating arguments with happy-talk distractions, and for trolls like Milo Yiannopoulos, it’s weaponizing hate, outraging people so they spread your message to the small, diffused minority of broken people who welcome your message and would otherwise be uneconomical to reach
*As to defense: *“Debunking doesn’t work: provide an alternative narrative."