sentences:  Since many South Korean websites require a valid resident registration number (RRN) in order to create an account, this presents many opportunities for identity theft and other types of fraud.For example, it was found that former South Korean president Roh Moo-hyun's resident registration number was used to gain access to hundreds of pornographic websites, as well as entertainment and gaming websites.Identity theft and other fraud is difficult to defeat in Korea, because each person's RRN is unchangeable, unlike other nation's identification numbers which can be changed if they are compromised (such as the United States' SSN).