Your modem and your Internet Service Provider (ISP) link your personal computer to the Internet. Traditionally, your ISP has provided you with a dial-up account which, using a regular dial-up modem and your phone line, allows you to:
More recently, ISPs began offering high-speed broadband service as an alternative to dial-up. One of the greatest conveniences of broadband service is that you're ready to surf or get your email at any time. Broadband access is available whenever your computer and modem are turned on.
All traffic on the Internet is routed according to a common protocol called IP numbers, also called IP addresses. Your Internet service provider assigns an IP number to your computer whenever you're connected to the Internet. This number identifies the route to and from your machine. [See Appendix I for more on your IP number.]
Many service providers assign one fixed IP number to each subscriber; some assign different IP numbers each time a subscriber connects. If you have a fixed IP number, your computer has a dependable "location" in cyberspace. If your ISP permits, your fixed IP number will allow you to run a home server with web, email, and other applications.
But if your machine is running a server, you also provide a dependable target for mischief. More on this shortly.
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