Apr 262013
 

Earlier this week I reviewed how to disable geolocation in web browsers. This feature allows location-aware websites to determine where you are located, often very accurately.

Whilst it can be very useful (e.g. when using Google Maps or to find local restaurant reviews without having to type in where you live), some people prefer to disable it in web browsers for privacy reasons.

However, regardless of whether you do or do not use geolocation services at home, it is likely that the publicly broadcast data from your wireless router is already stored in their databases – data from your router can then be used to provide other users with their exact location.

It is debatable whether the inclusion of your router in such a database poses a genuine privacy risk as the data stored is publicly broadcast via wireless i.e. any neighbor or passer-by could easily access the same data. However, few people are even aware that this practice happens on such an industrial scale so let’s take a look at how the process works.

How Your Wireless Router Is Used – Google Location Service (GLS) is one of the biggest providers – its database includes, amongst other factors, the GPS location of a wireless router and its MAC address.

The MAC address is a unique code which identifies an individual item of network hardware, distinguishing it from all the other millions of devices. Every wireless router has its own MAC address – and it is publicly broadcast, regardless of whether your wireless network name [SSID] is hidden or not.

Therefore, one way that GLS can map your router into its database is via Google’s camera cars (that help provide Street View maps). These cars are equipped with wireless receivers that can record the router’s broadcast MAC address and associate it with the corresponding GPS co-ordinates.

Another method is provided by any Android devices you use – if both Wi-Fi and GPS are enabled then the device can provide GLS with your router’s MAC address and its GPS position.

It should now be clear how data from your router is used – because GLS stores its unique MAC identifier and GPS position, it can provide a pretty accurate location to any requesting Wi-Fi device that is within range of your router, not just devices within your own home. [In practice, it’s a little more complicated as GLS may also use the known locations of other wifi networks that are in range to help triangulate the actual position of the requesting device].

How To Opt Out Of GLS – As I said earlier, it is not certain that there is any true privacy risk from allowing GLS to store your router data.

TinFoilHat

However, if you really do not want your router to be included in GLS you can opt out by changing the wireless network name (SSID) of your router so that it ends with _nomap.

E.g. if your wireless network name was ‘scooby’ you would need to change it to ‘scooby_nomap’.

If you don’t know how to configure the SSID of a router, see Step 3 onwards of our guide for help – it is best to connect to the router via a LAN/Ethernet cable as you would lose your Wi-Fi connection as soon as you change the SSID. Remember that you will need to re-connect any wireless devices you have to the new network name as it is has changed – you can reuse the same password unless you changed that too.

GLS will ignore data from any wireless networks it finds with the _nomap tag. However, your data would remain in their database until the next time their camera car passed by and found the _nomap tag, which could be years. To force GLS to find your new SSID far more quickly, use an Android device with Wi-Fi enabled to open Google Maps and use the My Location feature to establish a location fix in the vicinity of your wireless router. This will allow GLS to note your new SSID tag and remove your router from its database.

What About Other Geolocation Service Providers? There are several other providers (e.g. Microsoft and Skyhook) and it is highly doubtful that they take any notice of the _nomap tag, although they will certainly be able to see that identifier.

I can find no evidence that any other company respects it – they do not appear to offer any other opt out method of their own either.

Conclusion

Although it is possible to opt out of GLS, it appears you can’t opt out of competing services from Microsoft etc so any potential increase in privacy is limited. Also bear in mind that if everyone opted out then the service couldn’t provide as accurate data – even if you don’t use it at home you might benefit from GLS when travelling…