Sam Woolley wrote an article for the Open Technology Institute at the New America Foundation.
What is relatively new and on the rise is the cunning use of social bots by politicians, astroturf activists, and ideological extremists. These “political” bots and the messages they produce represent a new form of discriminatory computational propaganda. Via targeted spamming and other tactics, political bots drown out oppositional voices, demobilize activists, and promote the status quo.
For example, in South Korea, public servants in the cyber warfare unit of the Defense Ministry used bots to propagate messages in favor of President Park Geun-hye and Saenuri Party, including some which attacked political rivals. Though discerning the precise impact of these messages is difficult, their occurrence has heightened concern throughout the country: President Park won the election by a margin of a million votes.
The full article is available here.