Securing a wireless network--The basics--Part VI

Prevent Unintentional Roaming
Wireless networks are a bit like cell phones. Your cell phone ties to find the closest cell tower so that you can get the most bars of signal strength to have high-quality voice calls.

Wireless NICs work in a similar way in that they try to find the wireless router that has the strongest signal. The assumption is that the router it finds is yours because it is the closest and therefore has the strongest signal. However, that is not always true. If you have poor signal strength in a particular room of your house and your neighbor's router actually has a better signal in that room,, your wireless NIC might try to roam onto your neighbor's router, unless you instruct it not to.

You do not want your laptop unintentionally hopping over to your neighbor's wireless router whenever it sees a stronger signal or for whatever reason loses connectivity with your own router.

Using the Linksys NIC management utilities (such as WLAN Monitor), this is pretty easy. Simply do not add your neighbor's wireless SSID as a profile.

When using Windows XP to manage wireless connections, an additional step is required:

1. Bring up the properties of the wireless NIC. Click the Wireless Networks tab (See Figure 25 earlier). In the Preferred Networks section, click the Advanced button.
2. Make sure Automatically connect to non-preferred networks is unchecked (See Figure 26 earlier).
3. Click Close.
4. click OK (in the Properties dialog box).

Now, if the wireless NIC sees your neighbor's wireless router, it will not try to connect to it because it is not in the list of preferred networks.

Wireless Security Checklist
Wireless networks are extremely beneficial, but you must take some simple steps to protect them. Without taking the steps in this chapter, it is the equivalent of locking the front door and leaving all window and back doors unlocked and standing open. It is pretty easy (and so critical) to add appropriate security. Here's a quick checklist to refer to:

• change the password don the wireless router from the default (for example, admin).
• Change the SSID from the default (for example, linksys) to a random series of lowercase letters, uppercase letters, and numbers.
• Disable SSID broadcast on the wireless router.
• Enable WEP or WPA encryption on the wireless router and all wireless network adapters. Use the strongest encryption level that all devices support.
• Use a WEP or WPA passphrase that is a random series of lowercase letters, uppercase letters, and numbers.
• Disable ad-hoc wireless networking on all network adapters (applies to Windows XP).
• Disable auto-connection to nonpreferred networks on all wireless network adapters.

Summary
The steps in this chapter are really what most people need to keep their wireless network secure in all but the most extreme cases. The fact is that your SSID can be guessed or discovered, encryption schemes can be cracked (especially WEP), and MAC addresses can be spoofed (via a method called MAC address cloning); but this takes a great deal of skill, time, and money. If you want more protection than this, you can get it, but if you are still worried about wireless security, your best solution might be to stick with a wired network.

One additional wireless security measure that you can take that has not yet been discussed is MAC address locking (often called MAC address filtering). Because each wireless card has a unique identifier called a MAC address, and we know what the MAC addresses are for all of our wireless cards, we could instruct the wireless router to only accept connections from our cards and no one else's. This is called MAC address locking.

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