为了进行差错控制，必须对传送的数据帧进行校验。在局域网中广泛使用的校验方法是(7)校验。CRC-16标准规定的生成多项式为G(x)=X¹⁶+X¹⁵+X²+1，它产生的校验码是(8)位，接收端发现错误后采取的措施是(9)。如果CRC的生成多项式为G(X)=X⁴+X+1，信息码字为10110，则计算出的CRC校验码是(10)。要检查出d位错，码字之间的海明距离最小值应为(11)。

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Pharming is a scamming practice in which malicious code is installed on a personal computer or server, misdirecting users to(71)fraudulent Web sites without their knowledge or consent. Pharming has been called "phishing without a lure".

 In phishing, the perpetrator sends out legitimate-(72)looking e-malls, appearing to come from some of the Web's most popular sites, in an effort to obtain personal and financial information from individual recipients. But in pharming, larger numbers of computer users can be(73)victimized because it is not necessary to target individuals one by one and no conscious action is required on the part of the victim. In one form. of pharming attack, code sent in an e-mail modifies local host files on a personal computer. The host files convert URLs into the number strings that the computer uses to access Web sites. A computer with a compromised host file will go to the fake Web site even if a user types in the correct Internet address or clicks on an affected(74)bookmark entry. Some spyware removal programs can correct the corruption, but it frequently recurs unless the user changes browsing.(75)habits.

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