2012 NIS public opinion manipulation scandal

[4] In 2016, a prosecutors' investigation had turned up evidence that the NIS had effectively been orchestrating the activities of conservative groups since the administration of former president Lee Myung-bak (2008–2013).

The evidence shows that the NIS has been involved not only in political advertisements that conservative groups have run in newspapers but also in their plans to hold one-person protests and to hand out pamphlets.

Yoon sought the prosecution of the former head of the NIS, Won Sei-hoon, for violating the Public Official Election Act for his role in the case.

[7] In February 2015, Won was convicted on charges of instructing NIS officials to manipulate internet comments and sentenced to three years in prison.

[11] In December 2020, the National Assembly passed reforms curbing the powers of the NIS, explicitly banning the agency and its employees from interfering in domestic politics.