●Melissa and LoveLetter 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 and.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
（72）A．virtual
B．virus
C．worms
D．bacteria
（73）A．memory
B．caches
C．ports
D．registers
（74）A．names
B．cookies
C．software
D．extensions
（75）A．cracker
B．user
C．customer
D．client