Security Cameras: A Possible Security and Privacy Risk
by Ralph Brandt on Sep 25, 2009 with 2 Comments
Can that little camera that watches over your baby or your home be a threat to your security and privacy? The threat is not big brother but the neighborhood pervert.
I recently bought a small license plate camera for my car to be able to see better where I am backing. When I put the car in reverse the camera comes on, the monitor lights up and I see behind me. A couple days after I installed it I was driving along a road near my home. I was surprised when the display on the dash that is dark except when I back up came on. I saw a shot of the outside of a building I was passing. A mile further I saw a fuzzy picture of a baby in a crib! Over the last week I have seen the outsides of buildings, homes and businesses as well as some inside views and even people inside.
I am a ham radio operator and a long term techie so it was easy for me to see what was happening. My camera on the license plate is connected to the backup light. It transmits the signal by radio on the 2.4 giga-hertz (GHZ) band when the power to the backup light comes on. This means I did not have to run a wire from the license plate to the dash. The little monitor on my dash is plugged in all the time but it only turns on when the receiver gets a signal. Wireless baby monitors and security cameras also use the same frequency so they trigger my monitor if I am close enough. Several of these that are located outside can be seen for as much as five hundred feet from the camera and ones inside carry over half that distance. One is in a home that is not even on the road I am traveling.
Waves in the GHZ band travel line of sight. They can easily go through walls unless they are metal and they are short enough to pass through window openings. The .8 GHZ cell phone signals which are about 16 inches long go through car windows. At 2.4 GHZ the waves at three times the frequency are less than 8 inches long.
My monitor has a minimum antenna built into it which is not very efficient. It is just enough to get a solid signal from the back of the car. Far better antennas can be purchased or built that would extend the viewing range even further. Hams and commercial entities easily use the GHZ band for distances of twenty miles with very low power, good line of sight and high gain antennas on both ends. With a high gain antenna on the receiving end the distance would be much shorter but far over the five hundred feet I see. A twenty four db gain antenna is a structure a foot square and only a couple inches thick. This increases the signal more than two hundred times – it doubles for each three db. I haven’t opened the receiver but I am certain it is possible to disconnect the built in antenna (probably a coupling to the power cord) and connect an external jack to an antenna. With one of these antennas on my receiver and on a high spot I might “see” transmitters more than a mile away.
So the little camera that allows mom to watch over a baby from the kitchen could be providing an image to someone outside who you really don’t want to have access to your home. I would not throw out the unit but I would be careful what it is showing. Although it is possible to shield the house but that is a very expensive endeavor.
Note – added 10/2/09 I believe there is an effective way to jam these signals from at least one direction which is usually enough to prevent viewing by people in passing vehicles. Mount a second camera near the road and point it at the home. It must be away from the home and closer to the road. The second signal will either override or jumble the weaker signal from inside the home. This would not prevent someone from watching from the other side of the house or from a vantage point with a good antenna. If the camera cannot be placed far enough from the home it could interfere with watching the desired camera inside. It is the cheapest way to I can devise.
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Published in: Emergency Preparation
Westbrook | Sep 25, 2009 | Reply
It may surprise some that there are those who purposely cruise certain areas to tap into home and business monitoring devices, as well as wireless information from computers. Your article is a useful technical explanation of how wireless signals can be tapped into. Hopefully, the gist of your message is understood, that of knowing others can see what you are monitoring or sending by way of wireless communications.
Ralph Brandt | Sep 25, 2009 | Reply
I wish I could be more helpful in giving ways to prevent the abuse. I was pretty sure that people would be doing the cruising but hadn’t actually seen a report.
I’ve worked with radio from 3.5 MHZ to 3GHZ and have a pretty good grasp of propagation. I am not aware of any way to prevent this short of VERY EXPENSIVE shielding like maybe a grounded mesh cage. I personally prefer wired units. They MAY under some weird situations radiate info but it is far less likely.