3 Ways to Rein in Your Wireless Signals

Wireless networks have an inherent security threat: They transmit radio signals nonstop. However, by limiting the direction and range of those signals, you can improve the security of your network. The logic is simple: If an intruder can't pick up a useful signal, he or she won't be able to successfully connect to your network. You can use three basic methods to limit wireless network radio signals: adjust the output power of your wireless Access Points (APs), cover your walls and windows with specially made signal-confining coverings, and limit the direction in which your wireless antennas transmit signals.You can also use a combination of these methods. Here's how they work.

Adjust Your Power
First, let's talk about adjusting your wireless APs' output power. The FCC regulates the radio spectrum that wireless network equipment uses, including how much power a device can output during radio transmissions. A certain output power level equates to different signal strength levels at different distances: The farther away from the signal the receiver is, the weaker the signal strength will be.

Some, but not all, wireless-equipment manufacturers include adjustable settings in their firmware that let you set the radio transmitter's output power level. For example, a typical AP might output 20 milliwatts (MW) of power, and the firmware interface might let you turn up that power level to as much as 200MW. The AP might also let you turn down the output power to a setting as low as 1MW. By adjusting this setting, you're effectively adjusting the distance the signal will cover. You could feasibly reduce the output power in any given area where you use a wireless network without causing problems with authorized connectivity.

If your AP firmware doesn't let you adjust output power levels, you can install third-party firmware. Several third-party firmware solutions are available for various types of APs, including APs from ASUS, Buffalo Technology, Cisco Systems, Linksys, Motorola, NETGEAR, Siemens, and USRobotics. Consider, however, taking a close look at OpenWrt (http://openwrt.org), DD-WRT (http://ddwrt.gruftie.com), or Sveasoft's Alchemy and Talisman (http://sveasoft.com) AP firmware solutions. Each of these options is a reasonable choice (although OpenWrt is a bit tedious to use because it's modular in design, requiring you to add modules to gain various types of functionality). Keep in mind that not all firmware will work on all APs. You must review the associated Hardware Compatibility Lists (HCLs) to make sure the firmware has been tested successfully on your particular APs. Also, don't overlook the need to verify compatibility with different versions of the same AP models.

Third-party AP firmware is generally easy to install. Each product provides a simple Web-based configuration interface and gives you many extra features that your AP might not support with its original firmware. Keep in mind that, in some cases, using third-party firmware can void a hardware warranty or support package. If someday you need to return the hardware to the vendor, you might be out of luck.

Regardless of which firmware you use, when you adjust AP output power levels, remember that many factors affect overall signal reception. For example, a wireless workstation that's using a high-gain antenna could possibly pick up a very weak AP signal and successfully make a connection to that network. This scenario is possible because high-gain antennas amplify weak signals to make them more usable. These types of antennas also amplify the output signal during transmission back to the AP. Malicious users can use workstations with high-gain antennas to intrude on your network, even when those workstations are far from your APs. Many demonstrations have proved that such antennas can span distances of several miles! To combat this scenario, the second method of limiting wireless signals can come in quite handy.

Cover Your Walls
You can use special wall and window coverings to confine radio signals. Such surface coverings essentially prevent radio signals from moving through the surface to which you apply them. So, for example, you could confine a wireless network to one room or one department area. Likewise, you can prevent outside intruders from sending their signals in.

These surface coverings come in two primary types: a specialized type of paint that contains materials designed to reflect radio signals, or sheets of material designed for application either behind or on top of existing wall coverings. Both types of coverings can be expensive, and they require a considerable amount of work to install. Therefore, they might not be cost effective for your needs and budget constraints.

   Previous  [1]  2  Next