Build a wireless access point

With some open-source software, some hardware, and a lot of handiwork, you can make your own WAP.

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Before I tell you how to build your own wireless access point, I need to set one thing straight: You're not going to save money doing it yourself (although you won't pay much more than the price of an off-the-shelf WAP). But that's not going to stop me from showing you how to build a WAP on today's show.

Here are a few reasons why you should build your own WAP.

• You can highly customize how your WAP behaves.
• You'll learn how a WAP works.
• You can impress your friends with your skills.
• It's fun to put something together.

I use a small, inexpensive, commercial-embedded system board from Soekris Engineering. There are several software packages you can use, but I use an open-source application called m0n0wall. It provides a firewall and a Web-based configuration interface. And since it's open source, you can change it.

Wireless architecture and security

Treat all WAPs just as you do an Internet connection. They need to be protected from unauthorized use by your neighbors and passersby. The level of protection depends on what you're doing on the network, as well as the threat to your network. My how-to provides protection for most ordinary users, but I'll also tell you how you can easily increase your protection without much additional effort.

This project builds a combination firewall and WAP. If you're going to use the WAP in this how-to you can get rid of your current network address translation/firewall box, if you already have one. See the basic architecture where m0n0wall is the firewall and WAP.

M0n0wall will be set up to use WEP (wired equivalent privacy). WPA (Wi-Fi protected access) provides the best protection, but it hasn't been incorporated into any open-source projects. WEP has problems, but several mitigation strategies make it difficult (but not impossible) to successfully exploit a network using WEP with IV filtering.

If network security is of utmost importance, use IPsec in addition to WEP.

William Arbaugh is co-author of «Real 802.11 Security: Wi-Fi Protected Access and 802.11i.»