Actually there is a passive network tap inside with a cable going off to a computer in another room. At that other computer someone is eavesdropping or what is known at packet sniffing. The network taps make it easy to record from what you type on the keyboard to recording voip conversations. They require no power and can be made dirt cheap. The only shortcoming is that you have to be nearby to take advantage of it. It would be very easy if someone rented or had access to the office next door to use this device. They might have to punch a hole in the wall to access it unless there is some kind of socket nearby.
To record what is coming from the victims computer, some one might use a program like Wireshark. You can run multiple copies of it at a time to watch several connections. Ethereal was it's forerunner. Now there all kinds of software toolkits for network admins to use in their work. On major project is know as Backtrack. It especially excels at dealing with wifi connections.
Now a days these types of connections are almost obsolete, but you still have to be wary of them. There is actually some good uses for network taps to test software. Network switches are becoming so advanced that the passive network taps are no longer needed per se.
For a little more information see: http://www.instructables.com/id/Passive-network-tap-revised/
Note: Spinal Tap was a movie about a fictional rock band years ago. Sort of a spoof.