People today are mcreasmgly relymg on pubhc computer networks to conduct bUSIness
and take care of household needs. However, public networks may be insecure
because data stored in networked computers or transmitted through networks can
be stolen, modified, or fabricated by malicious users. Thus, it is important to know
what securIty measures are aVaIlable and how to use them. Network securIty practrees
are desIgned to prevent these potentIal problems. Network security, orIgmated
from meeting the needs of providing data confidentiality over public networks, has
grown into a major academic discipline in both computer science and computer
engineering, and also an important sector in the information industry.
The goal of network securIty IS to gIve people the hberty of enJoymg computer
networks wIthout fear of compromlsmg theIr rIghts and mterests. Network secunty
accomphshes thIs goal by provldmg confidentlahty, integrtty, non-repudIatIon,
and availability of useful data that are transmitted in open networks or stored in
networked computers.
Network securIty wIll remam an actIve research area for several reasons. FIrst,
securIty measures that are effectIve today may no longer be effectIve tomorrow
because of advancements and breakthroughs in computmg theory, algorIthms, and
computer technologies. Second, after the known security problems are solved, other
security loopholes which were previously unknown may at some point be discovered
and exploited by attackers. Third, when new applications are developed or new
technologIes are mvented, new securIty problems may also be created wIth them.
Thus, network secunty IS meant to be a long lastmg scuffle between the offenders
and the defenders.