Security+ Topic - Wireless Antennas and Power

I’m not sure I know of anyone who doesn’t use wifi.  It has become part of our everyday lives and without it I am not sure some people would know to cook.  When it comes to our homes, most of us will simply plug in an access point and we are good with the setup as long as we can get a signal in our living room.  In business, most IT departments will setup a distribution of access points to cover the entire area as seemless as possible.  Both of these are great strategies but there is another scenario that I would like to bring up as the normal setup provides an easy gateway for any attacker to monitor your wireless network.

I worked with a gentlemen that setup wireless communications between buildings for companies.  Now this sounds like a task that almost any IT person could accomplish but the reason he was contracted for it was that this connection needed to be secure.  Some of you may be saying at this point that they could just setup WPA2 and be done.  The little  bit of information here that is missing is the antenna used for the communication.  Generally, antennas will be omni-directional which means that the signal goes in every direction.  This is good for most setups but not for the ultra-secure setups needed by this company.  Antenna design is something that can go very in depth and I have experimented with designs as an amature radio operator so I will not be going into the details here except to give you an overview.

The antenna that needs to be used for this scenario is a yagi antenna that points the signal as much as possible in one direction.  This is not to say that the signal will be one hundred percent in one direction.  Signals will still propagate in every direction but the yagi antenna does a great job of focusing the signals in one direction.  Generally there will be a little bit of back-black of signal but it is not that big of radiation in the direction opposite of where you are pointing.  There are two benefits to this.  One being that signals can be pin-pointed to the target.  The second is that a yagi antenna can help extend the distance of the signal.  I encourage you to take a look into the yagi radiation pattern if this is something that sounds interesting to you.

Now comes the part of actually verifying that your antenna is doing what you want it to do by performing a site survey.  I personally use software called Heatmapper where I can import my own image (or floorplan) for where the signal is the strongest.  Basically you walk around the office clicking on where you are and the software creates a heat map of how strong the wireless signal is.  In the original application, it is good to see if every square inch of the office is able to get its wireless signal.  In the second part of this top, talking about a yagi, it can work wonders on if your antenna is working correctly by only giving signal in one direction.  Basically we are looking for an oblong shape of a signal and the heat map software will show strong signal in one direction away from the access point antenna.