Security for Microsoft® Visual Basic® .NET

Step 9: Secure the Network with a Firewall

In security terms, a network firewall is hardware or software that filters information passing through it. For example, you can put a firewall between a Web server and the Internet. This can be done physically with a hardware box—such as a LinkSys Internet gateway, where the Internet cable plugs in one side and the intranet cable plugs in the other side. This can also be done logically, with software such as the Windows XP Internet connection firewall. A firewall is used to restrict the flow of TCP and UDP packets based on the port they are using. A port is a 16-bit number embedded in a TCP or UDP packet. Different services choose different ports. For example, Secure Sockets Layer (SSL) communication ...