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The internationalized domain name (IDN) homograph attack is a way a malicious party may deceive computer users about what remote system they are communicating with, by exploiting the fact that many different characters look alike, (i.e., they are homographs, hence the term for the attack). For example, a person frequenting citibank.com may be lured to click a link in which the Latin C is replaced with the Cyrillic С. This kind of spoofing attack is also known as script spoofing. Unicode incorporates numerous writing systems, and, for a number of reasons, similar-looking characters such as Greek Ο, Latin O, and Cyrillic О were not assigned the same code. Their incorrect or malicious usage is a possibility for security attacks.〔("Unicode Security Considerations" ), Technical Report #36, 2010-04-28〕 The registration of homographic domain names is akin to typosquatting. The major difference is that in typosquatting the perpetrator relies on natural human typos, while in homograph spoofing the perpetrator intentionally deceives the web surfer with visually indistinguishable names. Indeed, it would be a rare accident for a web user to type, e.g., a Cyrillic letter within an otherwise English word such as "citibank". There are cases in which a registration can be both typosquatting and homograph spoofing; the pairs of l/I/1, i/j, and 0/O are all both close together on keyboards and bear a certain amount of resemblance to each other. ==History== An early nuisance of this kind, pre-dating the Internet and even text terminals, was the confusion between "l" (lowercase letter "L") / "1" (the number "one") and "O" (capital letter for vowel "o") / "0" (the number "zero"). Some typewriters in the pre-computer era even conflated the ell and the one; users had to type a lowercase L when the number one was needed. The zero/oh confusion gave rise to the tradition of crossing zeros, so that a computer operator would type them correctly.〔 Unicode may contribute to this greatly with its combining characters, accents, several types of hyphen-alikes, etc., often due to inadequate rendering support, especially with smaller fonts sizes and wide variety of fonts.〔 Even earlier, handwriting provided rich opportunities for confusion. A notable example is the etymology of the word "zenith". The translation from the Arabic "samt" included the scribe's confusing of "m" into "ni". This was common in medieval blackletter, which did not connect the vertical columns on the letters i, m, n, or u, making them difficult to distinguish when several were in a row. The latter, as well as "rn"/"m"/"rri" ("RN"/"M"/"RRI") confusion, is still possible for a human eye even with modern advanced computer technology. Intentional look-alike character substitution with different alphabets has also been known in various contexts. For example, Faux Cyrillic has been used as an amusement or attention-grabber and "Volapuk encoding", in which Cyrillic script is represented by similar Latin characters, was used in early days of the Internet as a way to overcome the lack of support for the Cyrillic alphabet. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IDN homograph attack」の詳細全文を読む スポンサード リンク
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