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Malicious Mobile Code by Roger A. Grimes

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Web Languages

The World Wide Web runs HTML, scripting languages, and object files (such as audio, video, graphics). Most of the coding is located on the web server and downloaded as needed. Scripting languages can run either on the web server (like CGI or ASP) or within the confines of the browser (like JavaScript). This section will focus on web languages that download and operate within the browser (client-side).

HTML

Web site documents are made up of ordinary text files conforming to the Hypertext Markup Language (HTML) standard. HTML is a subset of the larger Standardized General Markup Language (SGML) document specification in use long before HTML. A simple HTML file contains four components:

  • Text

  • Tags

  • Links

  • Other nontextual content

The text is the plain ASCII text you see displayed in your browser, or it can be used inside of tags as undisplayed code. Tags are contained within angled brackets <>, and are used to mark actions and format portions of the text. Often formatting tags come in sets of two: one to turn on a particular attribute and one to turn off the attribute. For example, <B>Malicious Mobile Code</B> in a web document would display the text, Malicious Mobile Code in a bolded format. Most HTML pages will contain a fair share of formatting tags to display even the simplest of text statements. Example 8-1 shows an example of HTML source code for a very simple web page.

Example 8-1. Example of a small HTML document

<HTML> <HEAD> <TITLE>Tiny HTML document</TITLE> </HEAD> ...

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