I contacted the guy responsible for the B2B LGMobile Support Tool on the J.A.U. website. Lets see what he aswers...
bruteforce wont help, it will take years...tried bruteforcing with a 4 characters password, no sucess, so the password must be longer than 4 characters, and that makes bruteforcing almost impossible.
Sony Xperia Z1 Compact - Stock