How Google uses WiFi networks to locate devices and how to avoid it: nomap

March 19, 2020, by Santiago Comment

If you enter the “Location” settings on your cell phone, you will see that the system offers you several methods to determine its position. The most complete and accurate uses the device’s GPS, in addition to the Location of WiFi networks and cell towers nearby. Google knows the location of those WiFi (including yours) and cell towers that surround you, because it has obtained them through crowdsourcing and from its Street View cars that have traveled the world collecting this and other information.

Add “_nomap” to your network’s SSID

As this did not seem entirely right to the authorities, they forced Google to establish a method for users to prevent their routers or WiFi access points and respective location from being indexed by the company, which consists of adding “_nomap” ( without quotes) at the end of the network name or SSID. For example, if my network was “android boss”, I should change it to “android boss_omap” so that Google does not save it and use it to determine the location of devices or “help apps like Google Maps work better”.

«_Optout», to block Microsoft

This legal pressure also affected other companies such as Microsoft, which implemented its own method, which consists of putting “_optout” somewhere in the name of your network. That is, if you wanted to prohibit both companies from registering the name and location of your WiFi network, you should put something like “androidjefe_optout_nomap” to your SSID.

I’m not sure if doing this is recommended. On the one hand, maybe you could prevent Google from knowing your location with better precision (or that of other people), which it could hand over to the authorities if they so requested (for example, in the case of a crime, where your location has something to see, even if you haven’t done anything at all). On the other hand, it could be counterproductive in case you want to locate your stolen or lost cell phone, in addition to avoiding collaborating with Google for the better functioning of services such as Maps, which serve to allow you to see things like your location history or the places where you’ve been before

Prevent your WiFi from being saved on Google servers

If you are concerned about your privacy, you probably also want to prevent Google from saving all the access points (and their passwords) to which you connect, as well as their location, on its servers, as we already saw.

Android saves all this data in your Google account by default. Makes a backup, which is useful in case you change phones. By restoring that copy, you will have all those WiFi access points back on your new mobile and you will not have to connect to them again and manually enter their password.

If you want to prevent this information from being saved by Google, you will simply have to deactivate that backup. The path should look something like System Settings, Cloud and Accounts, Backup and Restore. There you must uncheck the “Make backup” option.

I insist. This option allows you to easily migrate your WiFi networks and their passwords to another phone (or to the same, in case of a factory reset) after registering your Google account again, as well as other data, such as call log or application settings. If you deactivate it, you will lose this facility, although technically you should also be able to make a manual backup of all this information from the PC and the ADB tool, as well as the restoration.

References: Google, Android Police, Search Engine Land, TechRepublic

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