Reader Question: Is Someone Jamming My WiFi?

I recently received the following email message from a reader:

Hello,

I read some of the information you provided regarding Internet signals getting jammed intentionally and otherwise. Perhaps you can shed light on an issue. When our neighbors are NOT home, I can use a PC with wireless internet (set up in a room of my home facing their home) without ever getting knocked off the internet. When they ARE home, the signal repeatedly is lost. However, A laptop in another part of the home is rarely affected.

So I set up the laptop in the PC room and lost signals (when neighbor was home) on both machines (Provider rep. suggested I do this). Neighbor walks dog or otherwise is not on their property and there is no issue with signals. AND it is random. Usually neighbor comes in for lunch break and the Inet signal is lost.

Home from work and it is lost. I unplug wireless and it comes back. On and off. This is a new development (maybe two months. After the local police informed said neighbors to stop calling 911 to report bogus complaints on us, the signals began to drop. So we believe after police warned them to stop wasting 911 resources, they got a jammer and jam our signals at every opportunity to harass us. (Honestly, this is our first and hopefully last neighbor war. We don't know why they hate us so much but have been informed they hate everyone so we try not to feel too special.)

Question 1 - How can we test or otherwise determine the signals are being jammed (we are sure they are but need proof) and pin point the source? Prove or show great reason why the source is illegal.

Question 2 - How can we protect the signal from getting jammed?

Thanks for your insight.

I've written here in the past about the jamming of cell phone, GPS and Wi-Fi signals. Here's some ideas and possible answers to the reader's two questions.

Question 1 - How can we test or otherwise determine the signals are being jammed (we are sure they are but need proof) and pin point the source? Prove or show great reason why the source is illegal.

The best way to confirm someone is jamming is to use something called a spectrum analyzer. Wireless frequency spectrum analyzers are commonly used measure signals and interference. You could spend thousands of dollars on a full blown analyzer from a company like Agilent or use a 2.4 GHz USB spectrum analyzer from a company like MetaGeek. The company sells a 2.4 GHz analyzer for $99 that comes with software that will run on both PCs and Macs. According to MetaGeek, this analyzer will track all radio activity from any 2.4GHz device including WiFi, cordless phones, microwave ovens, Zigbee and Bluetooth. The software that comes with the device also graphically shows which channels to use and which ones to avoid. Here's more of when you would want to use a device like this from the MetaGeek website:

• If you install, maintain, or troubleshoot access points, find the open channel and minimize the interference.
• If you work with consumers, avoid a revisit by using a Wi-Spy in case they own a microwave or cordless phone.
• If you experience WiFi interference on a regular basis, discover competing access points.
• Conduct site surveys.

You could purchase one of these and, attached to your laptop running on battery, walk around your home looking for jamming/interference signals. If you want to get up unto the higher frequencies where the 802.11n devices have the option of operating (802.11n can use both 2.4 GHz and 5 GHz frequencies.), it will cost you quite a bit more money to measure interference. MetaGeek sells something called the Wi-Spy DBx, a 5GHz analyzer, for $599 that also comes with software.

You may also want to first try KisMac or iStumbler on an Apple machine or NetStumbler on a PC. These applications run on the computer and give you access point information including channels being used. Sometimes just swapping a channel can fix interference problems. For example, if your neighbor is using channel 6 you may want to change your access point to use channel 11.

Question 2 - How can we protect the signal from getting jammed?

If your neighbors are jamming your signal with a well designed jamming device, determining and using an open channel on your wireless access point won't work. If the jamming has been going on for a while chances are the jammer they are using functions only at 2.4 GHz. I'm I think the best thing to try (if you are currently running a 802.11g network) initially would be to switch over to an 802.11n access point and upgrade to 802.11n on your computers. If you have newer computers that may have 802.11n support built in.

You could run the 802.11n network at the higher 5GHz frequency which would be immune to the lower 2.4GHz jamming signals. This would be an inexpensive attempt that would also give you the bonus of much better network bandwidth and immunity from other interference sources (e.g some cordless phones, microwave ovens, etc) in you home.

I'm looking forward to hearing if this works.

WiFi Jamming and Defense

The most popular WiFi standards today, 802.11b and 802.11g, both operate in the 2.4 GHz (Giga Hertz) frequency band and are susceptible to interference from other products operating in the 2.4 GHz band including microwave ovens, Bluetooth devices, baby monitors and cordless telephones. 802.11n, currently in Draft 2.0 standard (with projected standard approval in the fall of 2008), can use both 2.4 GHz and 5 GHz frequencies.

WiFi signal jamming can be intentional using jamming or unintentional using devices that use the same frequency band. For example, if you live in an apartment or condominium with neighbors close by you could be unintentionally jamming their WiFi network every time you use your 2.4 GHz wireless phone.

Dedicated WiFi Jammers are extremely easy to find on the Internet and also relatively easy for someone with electronics and soldering experience to make. One of the more popular home-made jammers is called the Wave Bubble, a self-tuning, wide-bandwidth portable RF (Radio Frequency) jammer that is small enough to fit inside a pack of cigarettes. The Wave Bubble (also refered to as Wavebubble) is tunable and can be used to jam two-band systems such as cell and single-band systems like cordless phones, GPS, WiFi and Bluetooth devices.

Wave Bubble jamming frequency tuning is done by plugging the device into the USB port on a computer and entering the frequencies that are to be blocked. The user can even enter more than one frequency range and the device will advance to the next frequency in memory each time it is powered off and on. Wave Bubble output power is relatively low at .1 Watt for the high frequency bands and .3 Watts for the low frequency bands. Even at these low power levels, with a properly tuned external antenna, the effective range is about a 20 foot radius. With just the internal antenna range is significantly less.

Some of you are probably asking why I'm writing about this stuff - in my opinion it is no secret (try Googling "wireless jammers")....... and....... I have always believed that in any situation, in order to properly defend against an attack, it is important to understand as much as possible about the method of attack.

Now - regarding defense - the Daily Cup of Tech has a good list of tips to help defend against someone jamming your WiFi network. Here it is:

1. Always wire your access points. This way, you cannot be jammed from the server.
2. Wire access points directly back to the central switch and try to avoid bridging your connections. This will help prevent a cascade effect.
3. Do periodic audits of your “air space”.
4. Don’t broadcast that you are using wireless technology. Turn off your SSID on your wireless systems.
5. Do not place server rooms on an external wall. This could allow someone to jam your wireless link without even entering your office.
6. Catalog and label all server room hardware. Periodically audit your hardware lists.
7. Tightly restrict physical access to your server rooms.
8. Train all employees to immediately questions unaccompanied strangers in the office.

Once again - remember - these devices are illegal in the United States.