South Korea is in ONI's substantial category but is not on RSF's internet enemy list. South Korea's internet censorship policy is highly political and particularly strong toward suppressing anonymosity in the Korean internet. In 2007, numerous bloggers were censored and their posts deleted by police for expressing criticism of, or even support for, presidential candidates. This even lead to some bloggers being arrested by the police. Subsequently in 2008, just before a new presidential election, a new law legislation that required requiring all major internet portal sites to require identity verification of their users, was put into effect. This applies to all users who add any publicly viewable content. For example, to post a comment on a news article, a user registration and citizen identity number verification is required. For foreigners who do not have such numbers, a copy of passport must be faxed and verified. Although this law was initially met with public outcry, as of 2008, most of the major portals, including Daum, Naver, Nate, and Yahoo Korea, enforce such verification before the user can post any material that is publicly viewable.

Also, South Korea has banned at least 31 sites considered sympathetic to North Korea through the use of IP blocking.

Furthermore, search engines are required to verify age for some keywords deemed inappropriate for minors. For such keywords, age verification using national identity number is required. For foreigners, a copy of passport must be faxed to verify the age. As of 2008, practically all large search engine companies in Korea have complied with this legislation as well, including foreign-owned companies (e.g. Google Korea and Yahoo Korea)