为什么要禁止root远程登录

在实际工作中，公司的DBA都会设置禁止root用户远程登录，请问这是为什么?

  1. root是MySQL数据库的超级管理员，几乎拥有所有权限，一旦泄露后果非常严重;
  2. root是MySQL数据库的默认用户，所有人都知道，如果不禁止远程登录，可以针对root用户暴力破解密码。

实战案例

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select user, host from user;
+------------------+--------------+
| user             | host         |
+------------------+--------------+
| root             | %            |
| st               | %            |
| st0              | 192.0.12.111 |
| mysql.infoschema | localhost    |
| mysql.session    | localhost    |
| mysql.sys        | localhost    |
| root             | localhost    |
+------------------+--------------+
7 rows in set (0.00 sec)

mysql> update user set host='localhost' where user='st';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select user, host from user;
+------------------+--------------+
| user             | host         |
+------------------+--------------+
| root             | %            |
| st0              | 192.0.12.111 |
| mysql.infoschema | localhost    |
| mysql.session    | localhost    |
| mysql.sys        | localhost    |
| root             | localhost    |
| st               | localhost    |
+------------------+--------------+
7 rows in set (0.00 sec)

mysql> delete from user where user='root' and host='%';
Query OK, 1 row affected (0.02 sec)

mysql> select user, host from user;
+------------------+--------------+
| user             | host         |
+------------------+--------------+
| st0              | 192.0.12.111 |
| mysql.infoschema | localhost    |
| mysql.session    | localhost    |
| mysql.sys        | localhost    |
| root             | localhost    |
| st               | localhost    |
+------------------+--------------+
6 rows in set (0.01 sec)

mysql>