A wireless footprint is the area of coverage provided by a WAP or group of WAPs. If you’re planning to take the Security+ exam, you should have a basic understanding of troubleshooting security issues related to wireless networking.
Here’s a sample practice test question:
Q. Your organization maintains a separate wireless network for visitors in a conference room. However, you have recently noticed that people are connecting to this network even when there aren’t any visitors in the conference room. You want to prevent these connections, while maintaining easy access for visitors in the conference room. Which of the following is the BEST solution?
A. Disable SSID broadcasting.
B. Enable MAC filtering.
C. Use wireless jamming.
D. Reduce antenna power.
Can you answer this question? More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.
Wireless Footprint
The wireless footprint is the area of coverage provided by a WAP or group of WAPs. The following figure shows a diagram with six normal omnidirectional WAPs (labeled 1 through 6) and two directional WAPs (labeled A and B). The areas outlined with dotted lines indicate the radiation pattern of each of the WAPs, also known as their footprint. Although the omni-WAPs won’t have perfect-circle footprints as shown, this does give you an idea of their overall coverage.
WAP footprints
All WAPs are not wireless routers. In the organization depicted in the figure, these WAPs would typically not be wireless routers, but instead just plain WAPs. They would provide connectivity for the wireless clients to the wired network.
The two buildings are far enough away from each other and the organization chose to connect the networks using two WAPs with directional Yagi antennas. Because the Yagi antennas provide high gain and a narrow radiation pattern, it reduces the possibility of someone intercepting the signal unless they are directly between the buildings.
Remember this
Most WAPs use an omnidirectional antenna. In some situations, administrators use a high-gain directional Yagi antenna to connect two WAPs together. For example, you can connect two buildings with two WAPs using Yagi antennas.
Notice that the wireless coverage of WAPs 1, 3, 5, and 6 are all uniform. This indicates they have uniform power levels. However, WAP 2 has a smaller footprint, indicating it has a lower power level. In contrast, WAP 4 has a larger footprint, indicating it has a stronger power level. If you want to reduce the footprint of any WAP, you can reduce the power output because the amount of power used by the WAP determines how far it transmits. Use less power and you’ll have a weaker signal and a smaller footprint. Of course, the trade-off is reduced performance for authorized users. If the signal is weak, the negotiated speed is slower. Some users farther away from the WAP may not be able to connect at all.
You can also see that there are some dead spots that aren’t covered by any WAP. It would be possible to increase the power of all the WAPs to eliminate them. However, this increases the footprint and causes the wireless signal to transmit well beyond the boundaries of the building, which increases the overall risk associated with the wireless network.
Another method of changing the footprint is by modifying the position of the antennas. For example, if you position the antennas vertically (straight up and down), the signals radiate outward, increasing the footprint. However, if you position the antennas horizontally (parallel with the horizon or the floor), the signal radiates up and down more than it radiates outward. This is useful when transmitting a signal between floors of a building, and it also reduces the footprint outside the building.
Administrators have competing goals with the footprint. Users want easy access to the WAP, so users prefer a large footprint with strong signals. However, the stronger the signal is, the easier it is for an attacker to eavesdrop and capture network traffic. From a security perspective, the goal is to limit the footprint to prevent attackers from accessing the wireless network from external locations such as a parking lot, while also ensuring that users have adequate access to the WAP.
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Decreasing the footprint isn’t always successful at thwarting eavesdroppers. Most common wireless devices use omnidirectional antennas to receive a wireless signal from any direction. However, an attacker can create a directional antenna that can receive wireless traffic from a specific direction. For example, attackers create simple cantennas (antennas using a can) to capture signals from a specific direction. They connect the wireless receiver to one end of an empty can and simply point the can toward a wireless network. By pointing the cantenna in different directions, they can home in on the exact location of a wireless network. Additionally, they can eavesdrop on wireless conversations even though they are well outside the normal footprint.
Remember this
You can limit the range of a WAP to a room or building by reducing the WAP’s power level. This prevents people from connecting because they will be out of the WAP’s range.
Q. Your organization maintains a separate wireless network for visitors in a conference room. However, you have recently noticed that people are connecting to this network even when there aren’t any visitors in the conference room. You want to prevent these connections, while maintaining easy access for visitors in the conference room. Which of the following is the BEST solution?
A. Disable SSID broadcasting.
B. Enable MAC filtering.
C. Use wireless jamming.
D. Reduce antenna power.
Answer is D. Reducing the antenna power will make it more difficult for users outside of the conference room to connect, but will not affect visitors in the conference room.
Disabling service set identifier (SSID) broadcasting will require visitors to know the SSID and enter it in their device, making it more difficult to access the wireless network.
Enabling media access control (MAC) address filtering will block visitors until an administrator adds their MAC address.
Wireless jamming will prevent all mobile devices from connecting to the wireless network.
You may also like to view the blog post about Wireless Antennas.
