You have a firewall on your computer, so why not on your mobile phone and tablet too? A firewall enables you to control incoming and outgoing connections and to block those you don’t want. Here are three for Android.

Many apps access the internet without you knowing and while some obviously need to in order to work, such as social networking apps, email, messaging and others, some do not. In fact, you have to wonder what some apps are doing because internet access has nothing to do with their primary function.

Are they spying on you? Reporting usage back to who knows who somewhere on the internet? Should you be concerned if data is sent to foreign countries?

A true firewall would need to have root access to an Android phone or tablet, but here are three apps that work without root access. You just download them from the Google Play Store and run them like any other app.


NetGuard – no root firewall

Free, Marcel Bokhorst

NetGuard provides a way to prevent apps on your Android phone or tablet from accessing the internet. It is simple, straightforward and very easy to use. No special knowledge of firewalls, IP addresses and other technical details are required and anyone can use it.

It is not a true firewall, but instead it configures the phone or tablet with a VPN (virtual private network). All internet access is directed through the VPN and this gives the app control over what can connect to the outside world without requiring the device to be rooted.

This is a one-screen app and it displays a list of installed apps with two symbols on the right. The first one is Wi-Fi internet access on/off, and the second is mobile internet access on/off.

Each app can be expanded to show three additional settings and it is possible to block internet access when the screen is off, but allow it when the screen is on.

NetGuard Android firewall  NetGuard Android firewall

Many apps require internet access in order to work, like Facebook, Twitter, email, and so on. If you block internet access when the screen is off, it reduces the data and possibly the battery usage. This could be useful. When you need to use the app it will work normally because internet access is allowed when the screen is on.

There are lots of configuration settings and Wi-Fi and mobile internet access can be blocked by default, the default can be to allow internet access when the screen is on, you can select which Wi-Fi networks the blocking rules apply to, such as every network except your home network, and several more options.

NetGuard works well enough and turning off Wi-Fi access stops apps from accessing the internet. It also stops many apps from working too. In fact, there aren’t that many apps on my phone that work with no internet access. This means it is not able to prevent an app leaking personal data unless it will work completely offline with no internet access.

NetGuard is useful for limiting internet access by apps, such as when the screen is off. It does not increase security unless an app can work without internet access. Some can, but many can’t.


NoRoot Data Firewall

Free, Simple Good Mobile

NoRoot Data Firewall works in a similar way to NetGuard and it adds a VPN to the phone or tablet. All internet activity is then routed through the VPN and this enables it to allow or block internet access. It works on an app-by-app basis and this enables you to allow one app, but to block another.

One advantage of this app over NetGuard is that it is easy to configure global settings. The main screen lists all the apps installed on the device and there are mobile and Wi-Fi symbols at the top. Tap them and you can choose to allow all connections, allow foreground connections only, forbid all connections, enable or disable Wi-Fi or mobile.

Each app has separate settings for mobile and Wi-Fi internet access and you can block or allow them, or block background activity while allowing foreground connections. That last setting is a useful one and it prevents apps using up lots of data when it is not actually being used.

NoRoot Data Firewall is able to notify you when apps require internet access. They are blocked until you decide what to do with them – allow or block access. You have to keep an eye out for this or you will run an app and then wonder why it isn’t working. You must unblock it. As with NetGuard, completely blocking internet access for an app will often prevent it from working - what use is Facebook without internet access? Limiting internet access is possible though.

NoRoot Android firewall  NoRoot Android firewall

It is fascinating to see, when no apps are open and you have cleared memory, notifications appearing on the screen showing that apps are trying to access the internet. In fact, I turned off audible notifications because apps, even those supposedly not running, constantly access the internet and the phone was beeping every few seconds. Once the access permissions have been set, you won’t see so many notifications. They appear only while the app learns what is and isn’t allowed.

NoRoot Data Firewall keeps track of the data usage of individual apps. Android monitors mobile data, but it does not show Wi-Fi usage statistics. This app does and so you can see which apps use the most data. Rogue apps that use far too much data can easily be spotted and the apps list can be sorted by data usage.

You can view data usage on a chart that has hourly, daily, monthly and yearly usage views. Mobile data, Wi-Fi data and combined usage views are available. This is useful if you want to monitor data usage. Wi-Fi data is unlimited of course, but it can be useful to monitor it.

The app has the ability to filter IP addresses and domains, and you can build a list of items to be blocked. A night mode enables all internet access to be blocked at night and the start and end time can be set.

This is a useful tool for monitoring internet connections made by apps.


LostNet NoRoot Firewall

Free, LostNet Soft

Like the other two apps, LostNet NoRoot Firewall is not a real firewall utility, but instead is a VPN. This allows it to take control of the incoming and outgoing internet connections without the need to root the Android phone or tablet.

It lets you block internet access when an app is running in the background, which can save data when it is not actually being used. It has three internet options for each app, which gives you a fine degree of control, but apart from a firewall on/off switch, you cannot set a global access setting for all apps in one go. They must be configured separately.

LostNet can allow Wi-Fi only, allow Wi-Fi and mobile, or block all. It can block access to adverts in browsers and apps as well. I found some features a bit buggy and allowing adverts still blocked them, and blocking background access could block foreground access too. Rebooting the phone or tablet fixed some of these problems though.

The firewall has capabilities that are not in the other two apps. For example, it monitors the countries that apps access on the internet and it can block them. When the app is first run, it suggests blocking some countries, such as those where malware is frequently found to originate or access.

LostNet Android firewall  LostNet Android firewall

After using an app, you can open LostNet and view the countries that the app has accessed. Sometimes you see very strange behaviour that makes you wonder why apps are accessing certain countries. The number of countries they access is surprising too. Some apps access half a dozen different countries and you can see the amount of data sent or received. Why so many countries? It is very odd.

LostNet displays a list of regions around the world and each one has an allow and block setting. You can allow or block access to North Korea, Russian Federation, China, or whichever countries or parts of the world you think are unsafe.

Despite some glitches, LostNet NoRoot Firewall has some interesting features and it can control internet access by apps and limit the countries that are accessed to increase privacy and security.


The verdict

None of these apps is a real firewall and they are all VPNs. However, they do block outgoing connections to the internet and can prevent apps from accessing the internet when it is not essential. This can be used to reduce data usage, particularly on mobile connections, and it might increase battery life, although this is not guaranteed.

Some apps do not work if internet access is blocked, so it is not always possible to limit their activities.

NetGuard is different to the other two and it is simpler. It does not record internet usage and data transferred, but it does let you limit internet access. LostNet and NoRoot Data Firewall track data usage and they show which apps access the internet the most.

LostNet is the most interesting because of its ability to determine which countries an app accesses, and to block those with poor reputations. It can also block adverts to a certain degree, although the feature is labelled experimental in the app. It has all the features you want, but sometimes they don't work as expected. It's almost, but not quite perfect.