My Wordpress Website automatically creates files and modifies file permission hack

My wordpress website was hacked and blacklisted by Google. Later i found the causing file and removed it, changed FTP,admin, db passwords and also changed the file permissions by unchecking 'write' option. Now after a week i got a malware alert from GoDaddy's Sitelock and i checked my ftp and found new folders have added and file permission are automatically changed to 'write' (777). Now I am afraid that if google crawls my website again, it may get blacklisted again. Please help me what can be done to prevent hackers to enter my website.