Airport Extreme Base Station is being hacked/taken over

I've noticed that someone has been hacking and taking over my Airport Extreme Base Station and changing its name, I use strong passwords and this has happened once before.

Can anyone "see" my base station? As it's name is different than my network name.

Is there some security hole they have discovered?

Extreme version 5.7

Airport Utility version 5.6 (560.18)

Comcast cable internet

MacOS 10.7.5