Can open ports increase LAN exposure?
I have a Router on my LAN that connects all host PCs to each other. My router has an open port for Internet access, (and there will be an open port for my future remote desktop terminal connections). How exposed is my LAN? Can a port scanner see my router and its open port? Or is it only hosts whom I connect to that can become aware of my IP Address?

    Requires Free Membership to View

    SearchSecurity.com members gain immediate and unlimited access to breaking industry news, virus alerts, new hacker threats, highly focused security newsletters, and more -- all at no cost. Join me on SearchSecurity.com today!

    Michael S. Mimoso, Editorial Director

    By submitting your registration information to SearchSecurity.com you agree to receive email communications from TechTarget and TechTarget partners. We encourage you to read our Privacy Policy which contains important disclosures about how we collect and use your registration and other information. If you reside outside of the United States, by submitting this registration information you consent to having your personal data transferred to and processed in the United States. Your use of SearchSecurity.com is governed by our Terms of Use. You may contact us at webmaster@TechTarget.com.

In general, you should not have any open ports on the front of your router/firewall unless you're hosting a service (e.g. a Web site) on your local network that requires public access. Most small/home office routers come with a default policy that is configured to allow any outbound traffic and deny all inbound traffic. This is the desired policy, and I'd strongly recommend that you stick with it.

You mentioned a future requirement for remote desktop connections. If you do expose a remote management port, you should ensure that it's using a strongly encrypted connection or is tunneled through a virtual private network (VPN). If at all possible, you should also limit access to specific IP addresses, ones from which you expect inbound connections.

This was first published in September 2006