Using a mobile device such as a smartphone to act as a hotspot for a computer has become common practice. It’s handy for getting internet access on a laptop when it’s out of range of a Wi-Fi network, or perhaps to avoid using a Wi-Fi hotspot if you’re concerned about the security of the connection.

However, did you know the process can also be reversed? Reverse tethering, as it’s known, allows you to use your phone to provide an internet connection for your Wi-Fi-only tablet. Also, strange as it may seem, the process could also be used to provide an alternative connection for a smartphone or tablet that already has cellular access.

In spite of cellular data allowances and ever-growing 3G/4G coverage, there are several reasons why you might want to do this. You may be in an area with weak cellular coverage, or perhaps you’re wary of your data limits, particularly if you’re abroad.

If you’re considering setting up reverse tethering, be aware that it can be a fairly hands-on process, and in some cases can have security implications for your smartphone. Read on to find out more.

Android Devices

For Android devices, a hard-wired reverse tether without any additional equipment does require that you root your tablet or phone, and it's worth looking into the security risks associated with rooting first.

However, reverse tethering an Android device via USB to a computer directly by ethernet to a router does mean data can travel securely from device to computer and computer to router.

If your smartphone or tablet is rooted you'll need to have your device's USB driver installed on your computer, and to have downloaded the required Reverse Tethering .zip file found at XDA Developers.

With both of those acquired, and the USB driver installed, extract the Reverse Tethering.zip to a folder.

Then go into your device Settings, and under 'System' choose Developer Options. Enable USB Debugging and connect your device to your computer via USB.

If the USB driver is properly installed on your computer, you should see your device show up as 'Android Phone' expanding to 'Android Composite ADB Device' in your computer's Device Manager.

If so, open the Reverse Tether extracted and open Androidtool.exe. Once the interface opens, choose your device from 'Select a device' (your device will be the only one there and unrecognisable in name) and hit the 'Connect' button.

After a short while, and some additional installations on your smartphone or tablet, you should be connected to your computer's internet connection.

Again, root access is required as the functionality to complete reverse tethering is something that needs to be unlocked. Another method, using an app called USB Reverse Tethering found in the Play Store, also requires root access. Rooting isn't uncommon, but it's something which is best researched on before contemplating.

Using Windows

There doesn't seem to be any specific procedures for reverse tethering an iPhone, although it might be that jailbreaking a device might make it possible. Be careful though – Jailbreaking is a controversial area because the iOS ecosystem isn't open.  Apple has carefully designed its hardware and software to work 'as is', and doesn't support users tampering with or tweaking iOS to their own tastes.

However, Android users who don't want to root their device can reverse tether using tools available for Windows. Windows' inbuilt ICS (Internet Connection Sharing) could do a job sharing your internet connection via Wi-Fi or ethernet. However, for the first of those two a Wi-Fi adapter (additional to any already in use) is required. For the second, you'll need to connect devices via ethernet cables, which isn't easily done with tablets or smartphones.

Fortunately, there's a far more simple way. If you are using a Windows computer with an inbuilt wireless card or added adapter, a tool called Virtual Wi-Fi Router will turn that adapter into a hotspot, while leaving the computer connected to its active internet connection. Once installed, and avoiding bloatware during the process, you simply open the tool, choose a hotspot name, a passkey (WPA2 encryption is standard), the connection you want to share (ethernet, 3G or Wi-Fi), and hit Start.

Then, whatever smartphone or tablet you have will be able to see and use the virtual Wi-Fi connection. 3G and ethernet connections become securely accessible to your device, and while there may be little need to bridge a Wi-Fi connection you can do that also if you want to.

Mac OS

Apple has its own take on the virtual router idea, and it's built right into its Mac OS software. Found in System Preferences, users need only choose 'Sharing' and 'Internet Sharing'. From here you can choose which connection you want to share, and how you want to share it, i.e. share ethernet to Wi-Fi. If you then select 'Wi-Fi options', the hotspot name, the level of encryption and passkey details can all be specified.

Once confirmed, you will be asked if you want to start the connection, and once you do then your connection can be shared with your smartphone or tablet. Wi-Fi connections can't be shared via Wi-Fi because, unlike with Windows, such a connection can’t be used and shared at the same time.

About the Author

London-based technology writer and former deputy editor of Micro Mart, Kevin Pocock is a keen advocate for mobile device and data security. With a background in consumer computing, Kevin holds key insights into user experiences and is a regular contributor to mobilesecurity.com.