Location Guard Ng (UserScript)

Location Guard Ng is a rewritten version of the original Location Guard browser extension that uses modern web technology and is now a UserScript. It allows to protect your location while using location-aware websites, by either adding controlled noise or completely spoof with the fixed coordinates. It supports the following UserScript managers:

• Tampermonkey
• Violentmonkey
• AdGuard

Do note that AdGuard's userscript capabilities are limited (E.g. GM_addValueChangeListener and registerMenuCommand)

Installation

https://cdn.jsdelivr.net/npm/location-guard@latest/dist/location-guard-ng.user.js

TODO

• [ ] New configuration UI
  • The current configuration UI is back ported directly from the original browser extension. Need to rewrite in React and JoyUI.
• [ ] Per domain configuration
  • The original browser extension allows to set different privacy levels for different domains. This feature is not yet implemented in the UserScript version.

How to build

• Clone the repository
• Use pnpm to install dependencies (pnpm i)
• Run pnpm run build
• The built script will be available in dist folder

What is Location Guard and Location Guard Ng?

Websites can ask the browser for your location (via JavaScript). When they do so, the browser first asks your permission, and if you accept, it detects your location (typically by transmitting a list of available wifi access points to a geolocation provider such as Google Location Services, or via GPS if available) and gives it to the website.

The Location Guard browser extension project starts since 2013 and aims to intercepts this procedure. It has been discontinued in 2020 and now obsolete (due to the removal of MV2 support in Google Chrome).

The Location Guard Ng is a rewrite version of the original Location Guard browser extension that uses modern web technology (Like TypeScript, React, rollup, etc).

The permission dialog appears as usual, and you can still choose to deny. If you give permission, then Location Guard Ng obtains your location and adds "random noise" to it or even completely spoofs it with a specified fixed location. Only the fake location is then given to the website.

To see Location Guar Ng in action use this demo, a geolocalized weather forecast, or go to Google Maps and press the "pin" button.

What kind of privacy does Location Guard Ng provide?

Location Guard Ng provides privacy within a certain protection area by ensuring that all locations within this area look plausible for being the real one. This is achieved by adding random noise in a way such that all locations within the protection area can produce the same fake location with similar probability. As a consequence, the fake location provides no information to the website for distinguishing between locations within the protection area.

Warning: background knowledge can still be used by websites to guess the real location within the protection area. For instance, if the protection area is in the middle of a lake containing only a small island, it will be easy to infer that the real location is on the island. In scenarios like this you should choose a higher privacy level, or deny disclosing your location at all, or specify a fixed location.

What are "privacy levels"?

The privacy level determines the amount of noise added to your real location. A higher level adds more noise, so the fake location will be further away from the real one. This offers protection within a larger area, but it might make the service provided by the website less useful.

By default all websites use the "medium" level (this can be changed from the extension's options). You can select a different level for a specific website using the icon. For instance, you could select a lower privacy level for websites that need an accurate location (eg. maps), and a higher one for websites that only need approximate information (eg. weather forecast).

For more flexibility, each level can be configured from the Privacy Levels tab. The red circle is the protection area: locations in this area look plausible to be the real one (see "What kind of privacy does Location Guard provide?" above). The blue circle is the accuracy: the fake location will be inside this circle with high probability (note that the noise is random). Use the slider to adapt the two areas to your needs.

What is a "fixed location"?

The privacy level can be set to "Use fixed location". In this case Location Guard always reports to the website a predefined fixed location that never changes (instead of generating a fake location by adding noise to the real one). This offers the highest privacy, since the reported location is completely independent from the real one, at the cost of very low accuracy.

You can modify the fixed location from the extension's options (Fixed Location tab).

When using a fixed location, the browser's geolocation is not performed at all. This offers better privacy, since the list of wifi access points is not transmitted to Google's servers. However, it has the side effect that the permission dialog is not displayed at all. This behaviour is usually acceptable when the fixed location is dummy, but it can be modified if you wish.

Why some websites detect my location although I use Location Guard Ng?

Some websites detect your location based on your IP address which is visible to all websites you visit. However, most of the time this type of geolocation is not accurate and is limited to the city or postal/zip code level.

Location Guard Ng does not protect your IP address; it hides the location revealed by the browser through the JavaScript API, which is usually very accurate.

How Location Guard Ng uses my information?

Location Guard Ng takes your privacy seriously! First, the extension itself has no "special permission" to access your location, it can obtain it only when a website asks for it and only if you allow access in the permission dialog.

Location Guard Ng runs locally in your browser and sends no information whatsoever to the network. It only communicates your fake location to the website that asks for it.

Location Guard Ng also never stores your real location. The fake location is cached for a small period of time; if a website asks for your location during this time the cached fake location will be returned. This improves privacy by avoiding to generate too many fake locations which would be centered around the real one. The cache period can be configured from the extension's options (Privacy Levels tab) and there is also a button to delete the cache.

What is the technology behind Location Guard Ng?

Location Guard Ng implements a location obfuscation technique based on adding noise from a 2-dimensional Laplace distribution. This method can be formally shown to provide a privacy guarantee which is a variant of Differential Privacy. More details can be found in the CCS'13 paper, or in the PhD thesis of Nicolas Bordenabe.

Location Guard Ng © Sukka, Released under the MIT License. Authored and maintained by Sukka with help from contributors (list).

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