Korean Government Anti-Corruption Unit Accused of Spying on Journalists

This was always a concern that this agency would be used for partisan purposes by whoever was in charge at the time and that is what the opposition is claiming is happening now with the collecting of phone records of conservative media figures:

The state-run anti-corruption office is under fire over allegations that it searched through the phone records of reporters and citizens critical of the organization and the government. 

The agency claims that this was a due, legal process and that it only checked the information of those who had phone calls with some of the people it is investigating. However, there is speculation that this may expand into an illegal surveillance scandal.

When checking phone records, the investigation agency receives personal information including subscriber name, resident registration number and address from the relevant telecommunications company. If the person whose phone records were checked asks the telecommunications company, it has to inform them of the details of when and which investigative agencies have requested data within the past year.

According to local telecommunications companies, the Corruption Investigation Office for High-Ranking Officials (CIO) has asked for the phone records of at least 10 journalists from several conservative news outlets on multiple occasions. 

In detail, the CIO requested the phone records of six reporters from the Chosun Ilbo on 12 occasions from July to October, while it also rifled through the phone logs of three reporters from the Joongang Ilbo 11 times from May to October.

Korea Times

You can read more at the link.