据专家分析由于Internet　从建立初始缺乏安全的总体构想和设计，从而存在很多缺陷目前Internet面临的最主要的威胁有：(45)。

①计算机病毒

②通信线路被窃听

③拒绝服务攻击

④来自内部的攻击

⑤假冒合法用户

⑥对隐私权的侵犯，及媒体传播，欺骗敲诈等

(69)

(66)

(67)

(68)

(64)

All　computers　need　some　sort　of(71)(OS).　Tile　majority　of　modem　home　computers　use　some　form.　of　Microsofts　OS.　The　original　Microsoft　OS　was　called　DOS　though　most　computers　use　Windows.　Windows　comes　in　various　versions　beginning　with(72)x　then　95,　98,　ME　and　currently　XP.　A　few　computers　use　IBMs　O/SApples　Mac　uses　their　own　OS　beginning　with　OS　I　though　most　modem　Macs　use　version　x　or　x.　Apples　latest　version　is　OS　10.x.　In　the　past　large　companies　and　institutions　would　have　an　OS　design　exclusively　for　them　but　as　the　Commercial　OS　become　more　sophisticated　the　benefits　of　this　practice　is　becoming　less　apparent.　Some　computer　professionals,(73)(ISP)and(74)computer　users　use　an　OS　such　as　UNIX(or　a　variant　such　as　Linux),　Windows　NT　or　2000(Win2k)or　one　of　the　other　network　or(75)based　OS.

(62)

(63)

(61)

(66)is　a　collection　of　web　pages　connected　together　with(67).　Each　document　or　page　has　a　unique　address　that　allows　you　to　find　it　among　the　millions　of　other　documents　on　the　Web.　The　address　is　called　a(68)(URL)or　sometimes　a　Uniform.　Resource　Indicator(URL).　When　you　chose　a　new　link　by　clicking　on　it　or　by　typing　it　into　the　address　field　your(69)sends　a　request　for　that　document　and　displays　it　on　the　screen.　That　link　can　be　to　a　different　section　of　the　current　document,　another　document　on　the　same　website　as　the　original　or　on　another　website　anywhere　in　the　world.　Web　pages　are　designed　using(70)or　HTML.