The law firm Cheongchul's Shin Joon-seon attorney conducted an interview about ‘Beyond Post’ and ‘case law related to employee PC access’.

“Since it’s a PC provided by the company and it’s a work messenger, why can’t we access it?” Many corporate officials have such questions. Additionally, companies that thought “it’s okay because we obtained consent for personal information access when joining” are now confused after seeing the court recently recognize civil liability for unauthorized access to employee PCs.
The law firm Cheongchul's Shin Joon-seon attorney stated, “Recent case law shows that the form of punishment is expanding from criminal liability to civil liability, which requires companies to be more cautious,” and added, “Especially, even if employee consent has been obtained, it may not be sufficient with only general consent.”
Furthermore, he advised that “it is important to specifically define the purpose and scope of the investigation, and to ensure procedural legitimacy such as third-party attendance and record-keeping during the investigation process.”
For more details, you can check the published full interview.
Be cautious of changed case law… compensation for accessing employee PC