Nearly got busted
I was working at a large (not so now) aircraft manuf through the 80s and into the 90s
The network at the site I was based at was token ring. I had a store \ build lab where I used to hide away most of the day, in there I set up 2 PCs with network doom which we usually played after hours. One boring afternoon myself and the PFY decided to have a deathmatch, fired up the PCs and started playing. 10 mins later we get a panicked call from the help desk, something was flooding the network with IPX packets and they had had complaints that things were running slowly... realising it was us I said Id fire up my network diags and hunt the culprit down. Needless to say I sorted the problem but totally failed to find the offenders and hand them over.