Building Internet Firewalls, 2nd Edition

Chapter 15. The World Wide Web

The existence of the World Wide Web is a major factor behind the explosive growth of the Internet. (In fact, many of the newcomers to the Internet believe that the Internet and the World Wide Web are the same thing.) Since the first graphical user interface to the Web to gain widespread acceptance, NCSA Mosaic, was introduced in 1993, web traffic on the Internet has been growing at an explosive rate, far faster than any other kind of traffic (SMTP email, FTP file transfers, Telnet remote terminal sessions, etc.). You will certainly want to let your users use a browser to access web sites, and you are very likely to want to run a site yourself, if you do anything that might benefit from publicity. This chapter discusses the underlying mechanisms involved, their security implications, and the measures you can take to deal with them.

The very things that make the Web so popular also make it very difficult to secure. The basic protocols are very flexible, and the programs used for web servers and clients are easy to extend. Each extension has its own security implications, but they are difficult to separate and control.

Most web browsers are capable of using protocols other than HTTP, which is the basic protocol of the Web. For example, these browsers are usually also Gopher and FTP clients or are capable of using your existing Telnet and FTP clients transparently (without it being obvious to the user that an external program is starting). Many of them ...