In early 00's I got my first gig as a web developer for an oil company. They had no other developers. There was some kind of security incident, and the PHB (li

In early 00's I got my first gig as a web developer for an oil company. They had no other developers. There was some kind of security incident, and the PHB (literally) wanted to beef up security. For some reason, infosec was a kind of hobby for me, and I suggested (and volunteered) to install Snort as a company-wide wire tap. So, during a maintenance period I installed the tap and server where the cable came in. And it worked great! A month or so later, all network activity stopped working after a new server was plugged in. It took days to figure out that the cause was a duplicate MAC on the NICs of my Snort box and this new box - a real one in a million thing that I've never heard of since.