【网站百科】带你了解一下互联网上的门牌号——IP地址
IP协议是Internet Protocol（网络之间互连的协议）的缩写，在中文中简称为“网协”，是为了让电脑网络互相连接进行对话而设计的协议。
无论你的电脑是什么牌子，只要遵守了IP协议就可以跟因特网连通。可是，电脑连入了互联网，我们怎么区分属于自己的那台电脑呢？
别担心，我们的电脑连入互联网后都会被分配一个独立的IP地址，这个IP地址在互联网上是独一无二的。
请注意，IP地址用实心点相隔为4段，而且每一段的数字都是在0-255之间。所以，如果有人说他的电脑IP地址是265.8.234.67或45.187.67时，不用怀疑，他肯定说谎了。
可是，既然每台电脑的IP地址都是唯一的，为什么会出现以下的情况呢？
当我们关闭电脑以后，我们的电脑没有接入网络，就没有被分配IP地址。下一次，你的电脑再联网，互联网又会给你分配一个空闲的IP地址，所以，即使是同一台电脑，在不同时间使用时，也会拥有不一样的IP地址，只是在你联网的这段时间里，IP地址是固定的且是唯一的。
电脑有了IP地址，就跟住宅有了唯一的门牌一样，信息在电脑之间进行传输时就不会出现混乱了。如你的电脑要从某个服务器上下载一些资料时，你发出下载指令后，这些资料所属的服务器就会寻找你电脑的IP地址，然后乖乖地把数据包传送到你的电脑上。当然，如果你只有IP地址，却没有发出下载指令时，这些数据是不会传送的。
然而在因特网发展的早期，电脑在接收数据时，根本不需要通过用户的确定，这样，一些病毒就能轻易地攻击你的电脑。
在20世纪90年代，就有一种专门利用IP地址进行传播的蠕虫病毒。要是有一段IP地址上的一台电脑被这种病毒感染，这种病毒就赖在这段IP地址上不走了，还不断地往这个IP地址段上的所有电脑发送数据包，如果你的电脑系统恰好存在漏洞，那么，你的电脑就会不幸地被感染了。
看来，在电脑接收数据包不需要IP确认时，还真是不安全！不过，专业的防火墙的出现挽救了这一切，它可以对发往电脑的数据包进行监测，一旦发现异常，就会发出警报，还会将本机IP地址与可疑IP地址之间的联系自行切断，就从而保护电脑的安全，让你放心地在网上“冲浪”。
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