题目内容：
回答题：Melissa and Love Letter made use of the trust that exists between friends or colleagues. Imagine receiving an __（71）___from a friend who asks you to open it. This is what happens with Melissa and several other similar email __（72）___.Upon running ,such worms usually proceed to send themselves out to email addresses from the victim's address book, previous emails, web pages__（73）___. As administrators seek to block dangerous email attachments through the recognition of well-known ___（74）____,virus writers use other extensions to circumvent such protection. Executable （.exe） files are renamed to .bat an
D．cmd plus a whole list of other extensions and will still run and successfully infect target users.
Frequently ,hackers try to penetrate networks by sending an attachment that looks like a flash movie ,which, while displaying some cute animation ,simultaneously runs commands in the background to steal your passwords and give the __（75）__access to your network.（71） A．attachment
B．packet
C．datagram
D．message
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