What if I know for a fact I did not download anything except WoM, from worldofminecraft.net.
If you ONLY use WoM and NEVER EVER put your password somewhere else then you should be safe. This was mainly a SMP security issue where a TINY LITTLE DINOSAUR ARMS posted a fake flymod and harvested passwords. A password like ifhGdeuHHB646#%#bfeh wuold take tens of thousands of years to brtueforce so thats a sure bet though these password were phished. No ammount of complicated shit will protect you from that.
A few good tips that i employ are.
a) If a server has a stay logged in feature, use it. It help you identify a fake website since you won't be logged in. And if your aren't then check the URL.
b) Don't try to hack SMP. If you do chances are you will be entering your password into a key logger. Also if you make an account on third party minecraft related websites use a completely different password. Alot if accounts are stolen when those databases are leaked or sold. Curse.com is a good example.
c) If you use autofill on your browser, occasionally reset the saved passwords and resave only trusted ones. This will prevent the autofill from being a TINY LITTLE DINOSAUR ARMS and posting your passwords publicly somewhere they were meant to go.