When it comes to securing a wireless network, many people believe that MAC address filtering offers a reliable layer of protection.
It works kind of like a white list. Network managers can approve only devices with specific MAC addresses to connect to their network.
It is an effective way to keep intruders out. However, in practice, MAC filtering provides only a superficial sense of security and can be easily bypassed by anyone with basic technical knowledge.
Let’s break down why that is, and how you can actually secure your network against intrusion.
What Is a MAC Address?
The MAC in MAC address stands for Media Access Control.
A MAC address is a special 12-digit hexadecimal number that identifies a network interface card (NIC). For example, if your computer has both an Ethernet port and a Wi-Fi card, you have two NICs, and each will have its own unique MAC address.
Since MAC addresses are unique and tied to actual hardware, you can use them to control network access. This is done via MAC filtering.
What is MAC Filtering and How Is It Used For Security?
In MAC filtering, a network admin can set rules on the network access point (i.e., the WiFi router) that check incoming connection requests for the MAC address and only allow the ones that are whitelisted to connect.
The said whitelist can be easily created by physically going to each authorized device and checking its MAC address. Sometimes, a MAC address lookup on a connected device is enough too. With a MAC lookup, you can check whether the address is real, belongs to a registered device, was created and assigned by a valid company. You can also see if it belongs to a virtual machine.
This is how MAC addresses are used in security. But attackers still exploit weaknesses in MAC security. Let’s see in the next section.
How Attackers Exploit Weaknesses in MAC Security?
Unfortunately, while this sounds like a solid security measure, the flaw lies in the fact that MAC addresses are neither secret nor difficult to spoof. If an attacker knows the MAC address of a whitelisted device, they can spoof it and impersonate an authorized device to gain access to the network.
The simplicity of MAC spoofing makes MAC filtering nearly obsolete as a standalone defense mechanism.
There are many Tools available online that allow users to change their MAC address in seconds. A tech-savvy attacker can even use the command prompt/terminal to attach a different MAC address to all outgoing traffic.
Once an attacker clones a legitimate MAC address, they can access the network as though they belong there. This bypass is often undetectable without advanced monitoring tools.
As for finding ‘legitimate’ MAC addresses, that’s simple too. Most people keep their phone’s wifi to ‘auto connect’. An attacker only needs to use their own WiFi hotspot and turn it on without a password. The devices in range will try to connect to it, and the handshake will contain their MAC address.
Attackers can use packet sniffers or other tools to extract the address from the handshake and then clone it. This is why MAC filtering is simply not enough for network security.
Better Alternatives to MAC Filtering for Network Security
There are far better alternatives to MAC filtering when it comes to network security. In fact, you should only treat MAC filtering as a supplementary measure.
Better methods include the following.
- Passwords and Encryption protocols.
Instead of using MAC filtering, you should simply put up a password requirement to connect to your network. Password-protected networks use encryption protocols like WPA3, which secure communication channels to prevent snooping, and the password itself prevents unauthorized devices from entering.
- Network segmentation
If your network is connected to sensitive devices or servers, then you can use network segmentation to isolate sensitive systems. This can be done via firewalls if you want a software solution, or you can add a new router/switch to the mix.
Creating network segments means that even if one part of the network gets compromised, the other parts remain safe.
- Monitoring and intrusion detection
There are plenty of ways to monitor networks and detect intruders. Intrusion detection systems (IDS) like Snort and Zeek can monitor network activity and detect anomalies and signatures of viruses or intrusion attempts. Then they either cull the intruder themself or raise the alarm so that a network admin can do it.
Conclusion
So, to summarize, MAC filtering is only good enough to deter casual users who want to freeload on your WiFi. Anyone who is adept at network intrusion can easily bypass MAC filtering. That’s why you should use better security measures like encryption, strong passwords, network segmentation, and IDS. That way, you can better protect your networks.
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