What is MAC Address Filtering?

Most 802.11 (Wi-Fi) access points allow the network administrator to enter a list of MAC (Media Access Control) addresses that are allowed to communicate on the network.

This functionality, known as MAC Address Filterings enables the network administrator to deny access to any MAC address not specifically allowed onto the network.

This requires that every new device on the network have it's MAC address entered into the database as an authorized device.

On the other hand, most 802.11 (Wi-Fi) NICs allow you to configure the MAC address of the NIC in software.

Therefore, if you can sniff the MAC address of an existing network node, it is possible to join the network using the MAC address of that node.