The purpose of this study is to analyze the expressions that are designated as prohibited words on the internet, and to examine the strategies that are used by netizens to evade these prohibitions. Words that are prohibited on the internet are defined as "the language expressions that are blocked up writing and searching for a dignified language life, youth protection, and the preservation of public order in cyberspace." It is a new language culture and a taboo of the 21st century that has happened in cyberspace. The main body of this study consists of three chapters. In chapter 2, the concepts of taboo and internet prohibited words, and the interrelationship of them are examined. From this, in chapter 3 we analyze the types and examples of prohibited words by referring to some lists of prohibited words. The counter-strategies of speakers are verified in chapter 4. Through this process, we get to understand the taboo or the expressions that are prohibited in cyberspace. We learn the background of the prohibition of words from netizens, as well. In addition, we report on language use strategies and linguistic variations in the internet age by examining the countermeasures adopted by netizens against the prohibition of words.