MySQL anonymous user login

After a fresh install of mysql at our linux box server. I was able to login to mysql with any user which we didn't defined. 
[root@spica ~]# mysql -utest

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 5.1.61 Source distribution


Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.


Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.


Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.


mysql> quit
Bye

To fix you need to delete the blank user at the mysql.user tables.

[root@spica ~]# mysql -uroot -p

Enter password:

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 14

Server version: 5.1.61 Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| mysql              |

| test               |

+--------------------+

3 rows in set (0.00 sec)

mysql> select user,host from mysql.user;

+------+------------+

| user | host       |

+------+------------+

| root | 127.0.0.1  |

|      | localhost  |

| root | localhost  |

|      | meitnerium |

| root | meitnerium |

+------+------------+

5 rows in set (0.00 sec)

mysql> delete from mysql.user where user='';

Query OK, 2 rows affected (0.00 sec)

mysql> select user,host from mysql.user;

+------+------------+

| user | host       |

+------+------------+

| root | 127.0.0.1  |

| root | localhost  |

| root | meitnerium |

+------+------------+

3 rows in set (0.00 sec)

mysql> flush privileges;

Query OK, 0 rows affected (0.00 sec)

mysql> quit

Bye

[root@spica ~]# mysql -utest

ERROR 1045 (28000): Access denied for user 'test'@'localhost' (using password: NO)

[root@spica ~]#