It is a WHOIS search service provided by the Korea Internet & Security Agency as an open API.
WHOIS search,
In the event of a disability on the Internet, the domain name registrant,
It is a service that can check the information about the ISP and ISP of the domestic IP address.
[Source]
* Korea Internet & Security Agency (KISA WHOIS)
* Open API address: http://whois.kisa.or.kr