I think you've used same user and pass somewhere else as of fortunejack. it had happened to me too but it was on poloniex there were other users too who had lost money on polo.
it's not a good thing in my opinion hacked very harmful to others !!
is there anything to prevent ??
Yes there is use different username and password on each and every site, always enable 2fa on every site. i now have 2fa enabled on every site.(where it's available)