How to block apps on tablet from accessing the Internet while on tethering

Question

I use my WiFi-only tablet for turn-by-turn navigation. I either use wifi hotspot tethering or bluetooth tethering through my phone's data plan. (Or USB tethering once I get a Y charging cable.)

My problem is that my tablet apps run their background updates and syncs while I am tethered, consuming my limited data plan. The worst culprit is Google account autosync.

While most apps nowadays are wifi/3G-friendly, that is, they have a setting to do heavy downloads only on WiFi, they do not differentiate broadband wifi or my phone's wifi hotspot. The Play Store app on my tablet would particularly update large apps in the background while I am driving!

Answer 1

In Android 4.2 and later, you can tell Android which Wi-Fi networks are mobile hotspots. In the device Settings, go to the Data usage page, then open the overflow menu (the three dots in the top-right) and click Mobile hotspots. It shows a list of Wi-Fi networks known to the device: tick any that are mobile hotspots.

Then, when you're on a network that's ticked on that list, Android will tell apps that the device is on 3G. Any "Wi-Fi only" update settings in apps or in the OS will act accordingly.

In addition, if the mobile hotspot is an Android phone running 4.3 or later, the hotspot will communicate this to the tablet, so it will automatically treat that Wi-Fi network as a mobile hotspot, without any user intervention.

For earlier Android versions, certain apps (such as my app Showr) have similar settings to the Android 4.2 mobile hotspots page, allowing you to treat a Wi-Fi network as 3G within that app. This is less useful than the Android-wide setting, because not every app supports it, and you need to set it for each app individually, but it works just as well if you can't update to 4.2.

Answer 2

I found four partial solutions to this, with varying thoroughness:

1. Configure Tasker or Llama to turn off auto-sync.

See the question Auto sync only when connected to a specific wifi network. Instructions are similar for Bluetooth or USB tethering. This eliminates the background sync of Google apps such as Calendar, Contacts, Gmail, Maps, etc. All other apps, such as weather apps, could and would still update.

2. Set the Tethering AP as a "Mobile Hotspot"

This is a duplicate of "Treat certain WiFi networks as mobile/cellular". You would check your phone's hotspot AP name as a mobile hotspot. Reading off the screen,

Select the Wi-Fi networks which are mobile hotspots. Apps can be restricted from using these networks when in the background. Apps may also warn before using these networks for large downloads.

See Dan Hulme's answer for further information.

However for wifi-only devices the Google Play Store doesn't have a "Auto-update apps over only WiFi only" option. I don't know yet if the Play Store updates apps while on a mobile hotspot. Maybe. So I guess the solution is to keep app auto-updates off.

3. Use Bluetooth or USB Tethering

Bluetooth and USB Tethering are not Wi-Fi, so therefore apps that set to update only on Wi-Fi will not update while the tablet under Bluetooth or USB Tethering.

Turn off autosync, as per #1, and this appears as comprehensive as one can get....

However for wifi-only devices the Google Play Store doesn't have a "Auto-update apps over only WiFi only" option. I don't know yet if the Play Store updates apps while on bluetooth or USB tethering, so again I guess the solution is to keep app auto-updates off.

4. Enable/Disable a Firewall

The most thorough solution? If your tablet is rooted, then you can install a Firewall to block all internet access except the turn-by-turn navigation app. Then all you got to do is enable or disable this firewall.

See also Izzy's answer which mentions a VPN-based firewall.

Answer 3

For completeness the answer will also include everything some of which you already know.

I understand in your situation that the phone is not distinguishing from your hotspot style of Wi-Fi (using expensive data from a cell tower) to any other Wi-Fi connection that the data would be cheaper to use.

Manual and automatic methods

There are methods to both easily manually disable Auto-Sync, and methods to automate the disabling of it:

Automatic

• If connected to "Home WiFi", then Turn on Auto-Sync (less account data).
• If connected to "TeatherName WiFi", then Turn off Auto-Sync

Simple "scripters" like "MacroDroid", plus other simple "rules creators" can pull this off.

Example:

I mention these 2 because I could not program my way out of a paper bag, but I can make a few scripts, or rules, or constraints, using those methods. Probably tasker and automate-it could also perform these functions. Auto-Sync off is a "easy one".

In my short time with that Macrodroid app, I was also able to have it reliably recognise that specific Bluetooth devices are connected (keyboard), so that could also be applied to make a auto-sync change.

It can also use a "hotspot" trigger and actions , which won't do any good in your situation, because the hotspot isn't the device you need to control. That method would have to be applied to the hotspot machine, and some creative firewalling, that does not sound so easy.

Stopping Google Store auto updates Manually

To access the setting when your in the Google Play store application hit your menu button, and select settings.

Go to the Auto-Update section of the settings. Setting your apps to never auto update does mean that you have to manually update them, but that gives you the option to choose when the updates occur, giving you control,

The google play store settings for update applications can be set to update as follows:

A) Do not auto-update apps
B) Auto Update at any time
C) Auto update apps over Wi-Fi only

Manual updates at the google store are made easy When you select the play store icon, and go to My Apps section.

The google store sorts apps that have updates available to the top of the "My Apps" listing

By carefully adding updates to your device manually you can know if a specific update is causing problems.

Widget Auto-Sync switch

There are many "widget" programs that will add an icon on your home screen to disable Auto Sync easily.

Widget Manual Sync Starting

There are also Widget apps that have "Sync Now" button, with SyncNow syncing will be updated manually at the press of a button. On my machine this activity ends, after any needed sync is done.

Background Data from Apps
Manual settings

In the network settings you click on the mobile data

Clicking on the menu button to get to the settings. We can see the Restrict background setting, and the auto-sync data setting.

Automatic , Identifying a mobile hotspot for no background app data

In the above settings Mobile data / menu button / Mobile Hotspots

In the Mobile hotspot settings , you can select exisiting mobile hotspots , to restrict background app data.

Answer 4

As you indicated a firewall might do the trick, but you've got no root: You might wish to take a look at NoRoot Firewall and Mobiwol: NoRoot Firewall, which both claim to require no root (as their names indicate).

NoRoot Firewall works based on defined IP rules:

NoRoot Firewall requires NO ROOT. It protects your personal information from being sent to the Internet. NoRoot firewall notifies you when an app is trying to access the Internet. All you need to do is just press Allow or Deny button.

NoRoot Firewall allows you to create filter rules based on IP address, host name or domain name. You can allow or deny only specific connections of an app.

So this will probably not do, as it would apply to "everything". However, Mobiwol should fill the gap: it registers as a VPN, and explicitly claims: Disable background activity for selected apps

^{MobiWol: App-specific rules, settings, logs (source: Google Play; click images for larger variants)}

As a side-effect, you can see in the logs which apps connected where to, and might catch some performing suspicious activities ;)