How to: Use a Firewall to Block Full Screen Ads on Android

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Infopackets Reader Steve G. writes:

" Dear Dennis,

Thank you so much for your article on How to Disable Full Screen Popup Ads in Android! Lately I have been inundated with full screen ads appearing on my smartphone and I have no idea where they are coming from. I tried your suggestion in the article, which says to wait for the full screen ad to appear, then press the app button on my phone to see where the ad is coming from. The problem is that these full screen ads don't have a title, so unfortunately I can't tell where the ad is coming from. You also suggested using a firewall but I am not sure which one I should download. Can you please help? These full screen ads are driving me crazy! "

My response:

This is a great question. If my first article didn't help you figure out where the full screen ads are coming from, I have two apps that should most definitely help: App Usage and NetGuard.

Related: Do you have a tight budget? Do you use pay-as-you-go for mobile data? If so, be sure to read "Explained: Absolute Best way to Limit Data on Android"

Related: Need to extend your Wifi coverage at home or in the office? Read this: Explained: What is Mesh WiFi? vs Extender, Router?

Monitor Apps By Their Usage

The "App Usage" app works by monitoring which apps are currently in use (even if you're not using the phone), then it sorts that information by date and time. This is a great starting point in trying to figure out which app is sending you the ads. The reasoning here is that the app that is sending you ads must be "active" in order for it to send the ad to your phone, which means that "App Usage" should have logged this action. For the record, App Usage is also a great app when trying to figure out which apps are eating up your battery!

Block Apps using a Firewall

Another option is to block all your apps from using WiFi or data, then only allow the apps you use. The reasoning here is that the app which is sending you ads needs an Internet connection (whether it's WiFi or data) in order to download the ad to your phone, then display it. If you block this connection, then it can't send you any ads.

Using this method is considered a "blanket approach" as it lessens the number of possibilities as to which app is sending you ads constantly. Let's look at an example. Let's say you have 100 apps on your phone but you only use 10 apps regularly. If you used the firewall to block all 100, then only allow the 10 you use, then that means 90 apps are now taken out of the equation.

If you keep receiving ads on your phone after firewalling 90 out of 100 apps, then that means one (or more) of the 10 apps you allowed through the firewall is likely the culprit. On the other hand, if you don't receive any more ads, then that means one (or more) of the 90 apps you blocked with the firewall is likely the culprit. In the latter case, you won't know which app it is, so I suggest you start with App Usage first, then use the firewall approach.

I should also mention that NetGuard is also an excellent app to help you control your cellular data by preventing apps from eating your data, so I suggest using this all the time even after you've figured out which app is sending you ads!

Important Firewall Caveats

After I published this article, I received an email from a user stating that he was already using a firewall on his phone and wanted to know if adding NetGuard would conflict. The answer is: yes, it will.

As such, please ONLY USE ONE FIREWALL on your phone. If I had to choose which firewall is the best, I would say NetGuard wins hands down because (a) it's completely free, (b) has no ads, (c) is incredibly simple to use, and (d) it actually works!

Also, please don't forget - if you block an app with a firewall, the app may stop working properly if it's designed to use an Internet connection constantly, whether it's through WiFi or data. For example: if you block your email app from using WiFi and data, then you won't be able to send or receive emails. That said, if you allow ALL apps on WiFi and restrict the majority on data (when you're mobile) then that should be good enough for most cases.

How to: Use a Firewall to Block Full Screen Ads on Android

Below I'll explain how to use both the apps I just mentioned.

  1. I suggest you start with "App Usage" first as this will help you figure out which app is sending you the full screen ads. To begin, download App Usage from Google Play. Depending on which version of Android operating system you're running, you may need to give App Usage special permissions to your phone in order for it to monitor your apps properly. Just follow the instructions after it installs to complete the setup.
  2. Keep using your phone as you normally would and wait for the ad to appear.
  3. Once the ad appears, go to App Usage and look at the apps that were recently used, and make note. If you see something out of the ordinary - such as "peel smart remote" app being used when you didn't use it (for example), then this is likely the app causing you problems. Next, you can either wait until another ad appears and review the App Usage again, or you can uninstall the app you believe is causing you grief. If there is no option to uninstall the app, then you can tap "Force Stop" and disable the app as I've mentioned in my previous article. If that doesn't work then you can use a firewall to block the app - discussed next.
  4. If you still can't figure out which app is sending you full screen ads then I suggest you also install NetGuard. NetGuard uses a localized VPN to block apps from using WiFi and data. It does not actually use a VPN to relay your information to a third party server - the VPN is done internally for reasons I've explained in this article. You will be prompted to allow the VPN during the installation of NetGuard; allow it and follow the onscreen instructions.
  5. Once NetGuard has been installed, begin blocking all your apps, then allow the ones you want. To do so:

    a) launch NetGuard then click the main menu (the 3 horizontal dots at the top right). Next, select Settings -> Defaults (white / blacklist)

    b) make sure that "Block Mobile," "Block WiFi", and "Apply when Screen on" are all enabled
    d) go back to the main screen. By default, all apps using Mobile and WiFi will be blocked

    e) select only the bare minimum apps you want enabled and leave the rest disabled
  6. Continue using the phone as normal and wait to see if the full screen ads keep appearing. If you see ads, then refer back to App Usage to see which apps are being used. At this point you should have whittled down the number of possibilities to a handful of apps. Once you find the app, uninstall it if you can; if not try and Force Stop it, or you can simply block it with NetGuard.

I hope that helps!

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About the author: Dennis Faas is the owner and operator of With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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