I was the victim of a hack last year on poloniex because i didn't had 2FA turned on for a second. I bought a new phone so i had to migrate my google authenticator app from the old phone to the new. That's when i got hacked by an ethereum botnet. They stole about 10k dollar in ethereum (when it was still worth 40 dollar per coin) and left all my other coins alone. Exchanges can be dangerous!