My last infection (involuntary I am talking about) and also my first was with a fake av, called Ultimate Defender
This was the wallpaper it put on my desktop:
I remember I just got my first internet connection and realised most programs are paid, requiring serial number. What I decided to do is type on google <programName> serial number... I remember then downloading some exes. Because I was using Kaspersky 6 with HIPS and it was always asking me questions I don't know anything about, I was just Tray Icon -> exit... leaving myself unprotected.
For a day I thought this, together with its alerts is a genuine AV. I then learned on Kaspersky's viruslist (nowadays secure list) that this is a fake av. I could not remove it any way, that's how I learned to reinstall Windows. This is also how I got enthusiastic about security, spending ages reading threat writeups and testing malware myself. I've never been infected without my knowledge ever since.
I should thank its creators for pushing me into this industry actually, it's good money
