Web Security and Commerce

Netscape Plug-Ins

Although the two examples in the preceding section involved standalone programs, increasingly there is interest in using downloaded programs to extend the capabilities of web browsers. One way to do this is with helper applications , such as the RealAudio player. Another way is through the use of plug-ins.

Plug-ins were introduced with Netscape Navigator as a simple way of extending browsers with executable programs that are written by third parties and loaded directly into Netscape Navigator. One of the simplest uses for plug-ins is to replace helper applications used by web browsers. Instead of requiring that data be specially downloaded, saved in a file, and processed by a helper application, the data can be left in the browser’s memory pool and processed directly by the plug-in. But plug-ins are not limited to the display of information. In the fall of 1996, Microsoft released a plug-in that replaced Netscape’s Java virtual machine with its own. And PGP, Inc., is developing a plug-in that adds PGP encryption to Netscape Communicator’s email package.

Getting the Plug-In

Plug-ins are manually downloaded by the web user and stored in a special directory located in the Netscape Navigator program directory. The web browser scans this directory when it starts up to discover what plug-ins are available.

Two popular plug-ins are the Macromedia Shockwave plug-in, which can play animated sequences, and the Adobe Acrobat plug-in, which lets Navigator display PDF files. ...