XDA Developers on MSN

You need more network security if you're just using MAC filtering

MAC address filtering has long been included as a security feature in many consumer routers, allowing users to block traffic ...
Ars Technica

does mac filtering still work if the device has already connected to the Wi-Fi;

MAC filtering never really works. Anyone wanting to get on the wifi can just run a sniffer for a few minutes, find a MAC that is allowed and use it on their device. MAC filtering is useless. As for ...