I was writing on another discussion about rogue sysadmins and how they could access a network once they were no longer with the company. So I started to wear the "rogue sysadmin" hat and figured how could I access my network from outside.
I recently noticed that a couple of laser printers we have are wifi enabled. They are the HP Laserjet pro 400 / m401dw and
LaserJet CP1025nw color. Not only can you access the printers thru your wireless network, but THEY CAN BE AN WIFI AP that would allow a malicious individual to gain access to your network from nearby.
Now imagine this, you scan your network and all you find is your regular printers and pc's and other equipment that you allow on your network. Little do you know that the small printer on someone's office is an access point. With SSID disabled you could have a entry that would be hard to detect because there is no other strange equipment connected, just authorized equipment being used in unauthorized way.
WareZwolF found this material that show a lot more models with the same behavior. http://its.unc.edu/commtechnology/communication-technologies/networking/current-issues/wi-fi-problems-from-hp-printers/
Have you checked if you have any of these printer in your network? do they have wifi AP enabled and SSID disabled? I've read that you can disable it and enable admin passwords on some models but others go back to enabling wifi once they are rebooted.
I hope this opens up a healthy discussion on the subject.