Blocking Computers on the LAN

The hazard

Computers that are directly connected to the Internet obviously need good firewall protection. The normal firewall settings for computers connected to a local area network (LAN) through a router are less restrictive. That reflects the trusted status necessary for networking, printer sharing, etc.

If you want to preserve the integrity of a computer that you use for important transactions online, the trusted LAN presents a threat. Your secure computer could easily be attacked by any other computer on the LAN — say a guest computer connected by WiFi, or one connected by Ethernet that is used for wide-ranging adventures online.

More restrictive firewall rules are needed to block attacks from the LAN. You could do that by cascading another router between the LAN and the secure computer. The alternative is to use custom firewall rules, which requires networking expertise. However, the Windows 7 Network and Sharing Center can take care of it for you. All you need to do is select the "Public" network option.

It can be hard to figure out how to change a connection if it's already set to "Home" or "Work". Take a look at the link under "Network" (in bold type by the park bench) as shown in the image below. If it says "Home network" or "Work network," just click it and you'll be taken to the box with the three options as shown in the image above. Select "Public network" and you're all set.