I use Meta Mask wallet. But I wonder, is it possibble to be attacted by hackers any way? My MEW wallet was stolen, that's why this question is problem for me.
Of course it is possible. Heck even if you had paper wallet somebody can randomly get same private key and steal your coins along the way. Back to your question keep strong password on your metamask, always double check to which wallet you are sending to as there are computer viruses that can switch what you copy and paste. Hacker can obtain the metamask files if they are good and this is why you want strong password. If you are really paranoid go and buy hardware wallet for easy and secure solution.