Question: Is MAC address filtering really useful?
As you know MAC Address filtering can be configured on wireless router or access point to filter and allow only wireless adapters with MAC address in allowed list to join wireless network. If your wireless adapter’s MAC address is not in the allowed list, it cannot join wireless network with no connectivity, access local only or other network error.
This approach is useful if you deploy it on small home or office wireless network (I recommend it), but not so good for big network as it’s time consuming to maintain long MAC address allowed list.
Furthermore, this MAC address filtering can be overcome by advanced users with good networking knowledge or hackers, by using sniffing program to gather those MAC addresses that are allowed to join wireless network, and then configure the captured MAC address manually on his/her wireless adapter’s properties and join wireless network (we call it MAC address spoofing).
Having said so, this feature adds additional layer of security to protect wireless network especially for small network, just like you use additional padlock to lock your main door at home.
This is an example of enabling the MAC address filtering on the DD-WRT router management console by allowing two devices for connecting to wireless network only.