Hardware Drivers :: Unexpected Device Appearing In Devices And Printers

My friend happened to look in Devices and Printers, and in the Multimedia Devices section he had about 10 devices showing up that he never heard of. Six of them were computers with names that he had never heard of, the others were devices that we could not tell what they were.

I expect that these entries mean that at some time they were on the same network that he was on. Would that be correct?

If so, then it is a matter for concern because he never goes on public networks. He only goes on his network at home, and a network in a small office that he rents and shares with one other person. They have their own router with security set up on it, and that router is connected to an Ethernet jack that most likely goes to a switch on a network that also provides internet service to some other offices in the same building.

This computer is only about 2 months old, so these entries can't be too old.

When I looked at his computer, he was on his home network and all those other devices showed as Offline. I right clicked on them all and removed them. Would it be a good guess that perhaps the security of the network at his office was compromised, and those devices were connected to that network at some point?

I told him to monitor and see when they reappear, but he won't be back in that office for 2 weeks.