I noticed on my CS2 server that when operating the server, after some time the "status" command would list a bunch of odd player names, states like this:
---------players--------
id time ping loss state rate adr name
65535 [NoChan] 0 0 challenging 0unknown ''
65535 [NoChan] 0 0 challenging 0unknown ''
65535 [NoChan] 0 0 challenging 0unknown ''