Phishing attacks and credential dialog spoofing
Spoofing credential dialogs is one of the most obvious attack techniques used to steal credentials. I built my first proof-of-concept demos for that in the early 90s. Looking back, that was more than two decades ago for the Novell Netware operating system. It just had a simple basic text-based login screen.
At that time, I had just started to learn C and how to print and read information to and from the screen. I thought of creating a simple utility that would print out all the text of the actual Novell Netware login experience, and then prompt for the password.
The word phishing didn't even exist back then as far as I remember, but that's what it basically was. It was just simple proof of concept and not used to exploit anything, but to this day it keeps reminding me how basic, yet effective, the ideas behind these attacks are.
To this day, spoofing login screens is a very powerful technique to be aware of.