How Does A Router Protect My Computer?

by on October 17, 2006

Q: How does a router work to protect my computer and is a router better than a software firewall?

A: Don’t focus on whether routers are better or worse than software firewalls, ask yourself what does it add to your security posture. One of the tenets of Information Security is “Defense in depth”. This means adding layers of security to your system makes it more and more difficult for someone to attack your system and compromise it. Think of it as an onion, peel back one layer and there’s lots more to go before you get to the soft core!

Now to answer your question on how a router protects your system, it does this in a variety of ways:

1. Your IP address on the Internet is assigned to your router. Your router in turn assigns a non-routable private IP address (RFC 1918 explains the nitty gritty if you want to read it, just google “RFC 1918” for some light reading!) to your computer.

2. Your router will initially only allow traffic to be initiated from behind the router (i.e. your PC) out to the Internet. It won’t allow someone on the Internet to come in to your PC.

3. Some applications will require you to open a port from the Internet to your PC (Typically chat applications like IRC, or peer to peer applications such as Shareaza etc.). With every port you open, is added risk to your system. That’s why a software firewall in addition to the router is a good idea.

4. Your computer won’t be processing random packets from across the Internet (there is constant “chatter” as systems are scanning, ARPing and so on that will hit your IP Address). The router takes on this load and your PC is left alone.

5. Worms that attack based on a common service port (Such as RPC or other typical Windows vulnerable ports) should be blocked right at your router, unless you have forwarded that port to your system from the Internet.

One Response to “How Does A Router Protect My Computer?”

    Great answer! Thanks, well explained and specific.