The easiest way to filter WiFi devices is to use the Wireless Filter menu. However, there are times when you want to block specific devices via a script. This is particularly true when you need to manage device blocking for a lot of devices. Scripting also allows you to schedule blocking/filtering on or off, as needed.

• For a bridged environment (Media bridge/Ethernet-bridge/Ethernet to Ethernet) you'll need ebtables.
• For a routed environment (single router), you'll use iptables.

Given a MAC address you want to control, like: AA:BB:CC:DD:EE:FF you can filter in two ways:

# Block
/usr/sbin/ebtables -A FORWARD -d AA:BB:CC:DD:EE:FF -j DROP

# Unblock
/usr/sbin/ebtables -D FORWARD -d AA:BB:CC:DD:EE:FF -j DROP

# Flush (unblock all the defined references at once)
/usr/sbin/ebtables -F

NOTE: There might be additional ebtables in your system so be careful about flushing the full ebtable.

# Block Internet access (or any intra-vlan):
/sbin/iptables -I FORWARD -m mac –mac-source AA:BB:DD:EE:FF -j DROP

# Block any network activity, even services provided by the router (minidlna/webserver):
/sbin/iptables -I INPUT -m mac –mac-source AA:BB:CC:DD:EE:FF -j DROP

# Unblock (reverse) whatever command was issued by replacing “-I” with “-D”:
/sbin/iptables -D FORWARD -m mac –mac-source AA:BB:CC:DD:EE:FF -j DROP

# Flush
You don't do that for iptables instead, reboot the device

Nowadays, blocking MAC addresses can be tedious. Many devices use MAC randomization. MAC addresses can “change” freqeently.

For managing this, one alternative is to filter using hostnames.

For example:

# Block:
iptables -I FORWARD -s iphone-julie -j DROP

# Unblock:
iptables -D FORWARD -s iphone-julie -j DROP

Still, the kernel resolves the hostname to an IP address. A device with randomized MAC address will obtain a new IP address when reconnecting. This might function well, but only until the user restarts the device or just manually disconnects WiFi.

If you're very security conscious, you could trigger a “service wireless restart” for each new client connecting, but that would be disruptive to the general network.

For WiFi devices, perhaps the best way to limit access is to make them connect to a dedicated SSID, and enable/disable that SSID as needed. For details about this approach, see the HOWTO: Turning on/off radio elements from script.