For the better part of the 90s and early aughts, the sysadmin handbook said, “Filter your incoming traffic, not everyone is nice out there” (later coined by Gandalf as “You shall not pass”). So CIOs started to supercharge their network fences with every appliance they could get to protect against inbound (aka INGRESS) traffic.
In the wake of the first mass phishing campaigns in the early 2010s,