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Chapter 9: Wireless LANs
✓ If possible, increase your wireless beacon broadcast interval to the maximum
setting, which is around 65,535 milliseconds (roughly 66 seconds).
This can help hide the AP from hackers who are wardriving or walking
by your building quickly. Be sure to test this first, though, because it
might create other unintended consequences, such as legitimate wireless
clients not being able to connect to your network. For more specific
details on wireless protocols, check out Wireless Networks For Dummies
by Peter T. Davis and Barry Lewis.
✓ Disable probe responses to prevent your AP from responding to such
requests.
Use personal firewall software, such as Windows Firewall, on all wireless hosts
to prevent unauthorized remote access into your hosts, and subsequently,
your network.
Finally, don’t forget about user education. It’s not foolproof, but it can help
serve as an additional layer or defense. Ensure that security is always on the
top of everyone’s mind. Chapter 18 contains additional information about
user awareness and training.
MAC spoofing
A very common defense for wireless networks is Media Access Control (MAC)
address controls. This is where you configure your APs to allow only wireless
clients with known MAC addresses to connect to the network. Consequently,
a very common hack against wireless networks is MAC address spoofing.
The bad guys can easily spoof MAC addresses in UNIX, by using the ifconfig
command, and in Windows, by using the SMAC utility, as I describe in
Chapter 8. However, like WEP and WPA, MAC-address-based access controls
are another layer of protection and better than nothing at all. If someone spoofs
one of your MAC addresses, the only way to detect malicious behavior is
through contextual awareness by spotting the same MAC address being used
in two or more places on the WLAN, which can be tricky.
One simple way to determine whether an AP is using MAC address controls is
to try to associate with it and obtain an IP address via DHCP. If you can get an
IP address, the AP doesn’t have MAC address controls enabled.
The following steps outline how you can test your MAC address controls and
demonstrate just how easy they are to circumvent:
1. Find an AP to attach to.
You can do this simply by loading NetStumbler, as shown in Figure 9-16.
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