Database administrators should use the following guidelines to keep passwords secure.

MySQL stores passwords for user accounts in the mysql.user table. Access to this table should never be granted to any nonadministrative accounts. Passwords in the user table are stored in encrypted form, but in versions of MySQL earlier than 4.1, knowing the encrypted password for an account makes it possible to connect to the server using that account.

Passwords can appear as plain text in SQL statements such as GRANT and SET PASSWORD, or statements that invoke the PASSWORD() function. If these statements are logged by the MySQL server, the passwords become available to anyone with access to the logs. This applies to the general query log, the slow query log, the update log, and the binary log (see Section 5.3, “MySQL Server Logs”). To guard against unwarranted exposure to log files, they should be located in a directory that restricts access to only the server and the database administrator.

Replication slaves store the password for the replication master in the master.info file. Access to this file should be restricted to the database adminstrator.

Database backups that include tables or log files containing passwords should be protected using a restricted access mode.