Strange connections on Hotspot/Active

I could not figure out.I have a hotspot network running on 450g v5.1 rOS.My wireless access is not secure(I don’t use password).Somebody is trying to gain access on my network with clonning mac addresses.I am not sure that my network is secure or not.

Your advises?
hs_act.png

i think the client is connected to AP but its not authorized..