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June 11th – 15th, 2018 – Ethical Wi-Fi Jamming

In a previous article, we discussed a few Wi-Fi jamming techniques and mentioned that Wi-Fi jamming could actually be useful and even desirable. This article caused a lot of reaction concerning the legality and the morality of jamming. Indeed, random jamming is both immoral and illegal in most circumstances.

However there could be situations where a Wi-Fi jammer is useful, desirable, and even ethical. This article lists a few scenarios to illustrate our point.

Please note that this article stays off of any legal considerations. Regulations differ widely across the globe, and we are not competent to address the legal aspects. We urge caution and recommend consulting an attorney before engaging in any kind of activity which could result in service disruption.

Spectrum sharing

In 2012, there was an incident which occurred in a subway station in Shenzhen. The following is an extract from a newspaper article:

 

Service on a Shenzhen subway line was halted this week, reportedly because the system had been compromised by a Wi-fi signal operating on the same frequency.

The signal may have caused interference that interrupted services and possibly made the subway system vulnerable to cyberattacks, one expert said.

(South China Morning Post, 07 November 2012)

 

The subsequent investigation highlighted a few interesting facts. The subway signaling system was using proprietary wireless communications operating in the 2.4 GHz ISM spectrum. At this time of the day, the station platforms were crowded. Later measurements showed that almost everyone had a mobile phone with activated Wi-Fi. So many Wi-Fi devices looking for a connection and sending beacon requests resulted in an extremely noisy RF environment, causing saturation of the subway signaling system.

Fortunately, transportation signaling systems are very secure. For passenger security, in the absence of a reliable connection, the entire train line shutdown. This caused delays and resulted in customer complaints.

Now imagine the same situation with an appropriately configured Wi-Fi jammer operating in the vicinity of the crowded train platforms. Most of the time, the jammer is off, and thus travelers have access to Wi-Fi coverage in the station. When the subway signaling system tries to communicate information, the jammer is toggled on and silences more than 99% of the Wi-Fi traffic, resulting in a reliable connection. When the subway signaling is completed, the jammer is switched off and the Wi-Fi traffic is available to the general population.

Most data users would probably not even notice that the Wi-Fi service was temporarily shut down, just like they would not notice that their train was on time.

Limitation of EM exposure

Whether it’s factual or not, many people are concerned that Wi-Fi emissions may cause brain tumors. If there’s any doubt, people want to protect against this invisible threat when they are not using the service.

Interestingly, while most Wi-Fi access points allow the administrator to turn the wireless signal on or off from a password-protected management console, there is usually no easy way to do it.

What if a little low-power appliance with a single touch button could kill and restore the residential Wi-Fi service on demand? That’s what a Wi-Fi jammer can do, no wiring involved. You could also program an on/off schedule, or any kind of event-based Wi-Fi activation/de-activation.

Channel management

This one is more technical discussion. As many people know, there are several radio channels that an access point can use. For example, in the popular 2.4 GHz band, there are usually 13 channels numbered from 1 to 13 (in fact there could be between 10 and 14 authorized channels, depending on local regulations). Most non-technical users just leave their access point in its default configuration as long as the service is satisfactory. Others try to adjust the channel and select a channel with the least number of users.

But there’s a catch: channel centers are 5 MHz apart, but the channel bandwidth is 22 MHz or so. Yes, channels do overlap, and quite a lot. What does this mean? That the devices in channel 2 and 3 are actually interferers to the devices in channel 1. There are actually only 3 non-overlapping channels out of 13. These are channels 1, 6 and 11.

Imagine your access point operates on channel 6, but there is another neighboring access point in this channel. How critical is that? Very little in fact. The medium access procedure of the Wi-Fi standard ensures that multiple devices can share the channel capacity in a fair way allowing equal access for each user.

However, in certain saturated conditions a user might be tempted be to switch to a less crowded channel, for example channel 7. The issue is that channels 6 and 7 overlap. The access points in channels 6 and 7 would probably interfere with each other, with the medium access procedure of the Wi-Fi standard being able to manage the situation only partially. The likely outcome would be collisions, lost data packets, retransmissions, leading to delays and reduced capacity and therefore user dissatisfaction.

Although a user can make sure they make the best decision for their access point, they don’t control how the other access points are configured. In the context of a corporate network, this can be a real problem during the deployment or maintenance of good Wi-Fi coverage. Neighboring access points could unexpectedly interfere with each other unless careful planning is used when deploying the network.

A Wi-Fi jammer can mitigate the aftermath of poor channel planning. It can ensure that only non-overlapping channels are used by entirely muting the other channels. It would also limit the possibility of rogue access points operating in unauthorized channels. It is also possible to selectively jam a rogue access point.

Conclusion

We have listed a few scenarios where we think a jammer is beneficial, without causing harm. This is what we would call ethical jamming. Again, the legal implications are not considered here. Jammers, especially channel muters and Smart Jammers are powerful devices, but with great power comes great responsibility: a jammer should never be used to randomly block other Wi-Fi equipment but can be used in an ethical way to increase security and user satisfaction.

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