Creating an Access Point

I remember reading about a penetration test where the testers went inside the HQ, plugged a device into the wall, labeled it as "IT DONT TOUCH" and then proceeded to connect to that device from a great distance to further attack the wifi network inside the building. Unfortunately I forget from where I read this, if any one knows what I'm talking about, please discuss it because I am trying to learn more about this and I would like to find that article but don't know what to search for.