2015职称英语理工类阅读理解文章及练习(四)

　　people tend to think of computers as isolated machines,working away all by themselves.some do-personal computer without an outside link,like someones hideaway cabin in the woods.but just as most of homes are tied to a community by streets,bus routes and electric lines,computers that exchange intelligence are part of a community m local,national and even global network joined by telephone connections.

　　hacking,our electronic-age term for computer break-in,is more and more in the news-brainy kids vandalizing university records,even pranking about in supposedly safeguarded systems.to those who understand how computer networks are increasingly regulating life in the late 20th century,these are not laughing matters.a potential for disaster is building: a dissatisfied former insurance-company employee wipes out information from payroll files.a student sends out a virus,a secret and destructive command,over a national network.the virus copies itself at lightning speed,jamming the entire network thousands of academic,commercial and government computer systems.such disastrous cases have already occurred.now exists the possibility of terrorism by computer.spoiling a system responsible for air-traffic control at a busy airport,or knocking out the telephones of a major city,is a relatively easy way to spread panic.yet neither business nor government has done enough to toughen its defenses against attack.for one thing,such defenses are expensive; for another,they may interrupt communication the main reason for using computers in the first place.