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MAC Address: What is it?

Jul 16, 2018 · 5 min read

MAC Address: What is it?

IP addresses identify you online, but there’s another layer of identification that most people don’t know about. There’s a label assigned to every device that can be exploited to track its location, and it’s called a MAC address.

How MAC addresses work

It all starts with a little piece of hardware called the Network Interface Card, or NIC. This is the piece of circuitry that allows your device to connect to a network. The NIC manufacturer provides each one with a unique MAC address. This is why MAC addresses are also sometimes called burned-in or hardware addresses.

The MAC address is an essential part of how network devices interact with one another. When you connect to a WiFi router or directly to your building’s ethernet, your device will send its MAC address through to form a connection with the next device along the chain. The next device will then send its own MAC address further along the chain, thereby building your connection to the internet, link by link.

MAC addresses also look different from IP addresses, and you’ll never get the two confused once you learn how to tell them apart:

IP address

For a good example of what an IP address is, just click here to see your own IP address!

MAC address

Most MAC addresses consist of 12 letters or numbers across 6 pairs. Examples:

Below, you’ll also learn how to find out your own devices’ MAC addresses, so keep reading!

Does your MAC address make you vulnerable?

Your MAC address is generally fairly secure, but it can be turned against you to monitor your location, disrupt your internet access, or even perform a man-in-the-middle attack. However, all of these approaches are fairly difficult to implement, and there are easy ways to counter them.

Tracking people using MAC addresses

Companies and institutions have used MAC addresses to track device locations. As a device (and the person carrying it) moves from WiFi point to WiFi point, it continues to broadcast its MAC address in order to connect to new WiFi points. In a large facility (like an airport) or a city, a unified WiFi system can be used to track users’ locations and gather information about their movement.

Doing this, however, requires access to a lot of WiFi points – something usually only available to large companies or institutions. The uses of MAC address tracking aren’t always very sinister, either – in some parts of the world, they are simply used to gauge traffic speed and flow.

However, there are also examples of abuses. In 2013, an advertising company in London was found to be using trash cans with WiFi to detect and track MAC address movement throughout the city, flashing targeted ads in response to the device’s movements and habits.

Disrupting or impersonating your connection

A hacker attempting to connect to the same WiFi router as you could use special software to discover your MAC address. If your router is set up poorly, they may even be able to impersonate you and hijack your credentials.

Some routers use MAC addresses to filter access, which can be a powerful security strategy when combined with other techniques. On its own, however, it is highly susceptible to MAC spoofing. All a hacker needs to impersonate you is your MAC address, which your device broadcasts regularly when looking for or making a connection.

Having a secure password-protected and encrypted WiFi router, however, will resolve this invulnerability. A hacker can still determine and use your MAC address, but they won’t be able to do anything as long as they can’t log in to the network as well.

How to protect your MAC address

It’s difficult to effectively use your MAC address to attack you. Your devices’ MAC addresses are difficult to tie to your identity, they almost never travel beyond the very first network device they connect to, and it’s rare to find yourself in a situation where a hacker could use it to attack you.

However, in the wrong situation, it can become a vulnerability. In addition, some local networks, like the one at your job or school, can use MAC address filtering to block certain online content.

Completely blocking your MAC address isn’t really a good idea, since without it, you won’t be able to connect to any other network devices and go online. However, there are a few different techniques you may want to use with your MAC address to stay secure or private.

Turn off WiFi when on the move

As you know, your MAC address can be broadcast to potentially hundreds of devices while you walk through a city. Even if you’re not connecting to any of them, your device still sends its MAC address to discover surrounding networks and list them for you.

If you’re a responsible and security-minded WiFi user, you only connect to networks you trust or when secured by a VPN. If that’s the case, you’ll have little to lose by disconnecting your phone’s WiFi feature when you travel, only turning it on when you need it or when you know your connection will be secure.

On some mobile devices, you’ll also enjoy the added benefit of prolonged battery life. After all, constantly scanning for connections and sending your MAC address all over the place can be taxing!

MAC spoofing

This solution will be different for every device, but it can be one of the best ways to secure your device. When you spoof your MAC address, you basically assign a made-up address to your NIC. The exact process will be different depending on the device whose MAC you want to spoof, but the basic steps are the same:

  • Find your current MAC address;
  • Use a built-in feature, an app, or a command prompt to change your MAC address to a specific address or a random one based on your MAC address’ format;
  • Check to see if your MAC address has changed.

Don’t forget that this process may disable anything that requires your device to have a set MAC address. If you’re connected to a router that has whitelisted your MAC or to a broadband cable that only allows a certain number of devices to connect, changing your MAC may disrupt your connection.

MAC spoofing can also be part of a hacker’s toolbox, so some system admins may not be too happy if they can see it being used. Use this method with caution!

MAC randomization

Instead of setting a single fake address, MAC randomization lets you cycle through random fake addresses whenever you aren’t connected to a WiFi address. As soon as you connect to a WiFi network, the randomization stops in order to maintain a steady connection.

As far as MAC security is concerned, this is probably the best sweet-spot. It protects your MAC address from being distributed randomly but doesn’t prevent you from making the connections you want to make. The way you’ll implement randomization, however, will depend on what device you’re using.

Different devices perform MAC randomization differently, and not all of them are actually capable of doing it. As of iOs 8, iPhones come standard with MAC randomization. Windows 10 PCs have the function built-in but disabled, and can actually remember different random MAC addresses for different WiFi connections. I suggest Googling the instructions for your device for the best results.

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Daniel Markuson
Daniel Markuson successVerified author

Daniel is a digital privacy enthusiast and an internet security expert. As the blog editor at NordVPN, Daniel is generous with spreading news, stories, and tips through the power of a well-written word.

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