[SinceBestThen]

I scanned my local network with nmap on Armitage and all devices except the routers all just had black screen and said "null null null" when I put my mouse cursor on them.

Is it because they are macbooks? lol

[Play Boy]

I don't have too much experience running Armitage but it's possible the "null" value being returned is due to the packet being dropped. The packet could be dropped due to a firewall dropping the packet. Try disabling the firewall and running a port scan then. Also try turning host discovery off if you have it on during your scan.