This is not fault of myetherwallet. This is just wallet not a safe, you are supposed to keep your coins secure.
This is not fault of myetherwallet but us. Like me, not think about the security, i used my own laptop, I think it is secure enough, in fact someone can steel my asset from remote area. Never download any wallets from untrusted new coins, that gives free coins or small tasks with big rewards. I think I wast trapped by the trick.