MySQL Secure Deployment Guide  /  Installing Connection Control Plugins

Chapter 9 Installing Connection Control Plugins

The connection-control plugin library enables administrators to introduce an increasing delay in server response to connection attempts after a configurable number of consecutive failed attempts. This capability provides a deterrent that slows down brute force attacks against MySQL user accounts. The plugin library contains two plugins:

  • CONNECTION_CONTROL checks incoming connection attempts and adds a delay to server responses as necessary. This plugin also exposes system variables that enable its operation to be configured and a status variable that provides rudimentary monitoring information.

  • CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS implements an INFORMATION_SCHEMA table that exposes more detailed monitoring information for failed connection attempts.

To install the connection-control plugins:

  1. Add these options under the [mysqld] option group in the MySQL configuration file (/etc/my.cnf):

      Loads the library each time the server is started.

    • connection_control=FORCE_PLUS_PERMANENT

      Prevents the server from running without the CONNECTION_CONTROL plugin, and server startup fails if the plugin does not initialize successfully.

    • connection-control-failed-login-attempts=FORCE_PLUS_PERMANENT

      Prevents the server from running without the CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS plugin, and server startup fails if the plugin does not initialize successfully.

  2. To verify plugin installation, restart the server and examine the INFORMATION_SCHEMA.PLUGINS table or use the SHOW PLUGINS statement:

    $> systemctl restart mysqld
    $> cd /usr/local/mysql 
    $> bin/mysqladmin -u root -p version
    Enter password: (enter root password here)
           WHERE PLUGIN_NAME LIKE 'connection%';
    | PLUGIN_NAME                              | PLUGIN_STATUS |
    | CONNECTION_CONTROL                       | ACTIVE        |

Configuring Connection Delays

Configure the server response delay for failed connection attempts using these server parameters:

Add these options under the [mysqld] option group in the MySQL configuration file (/etc/my.cnf) so that you can adjust them later as necessary. The default values are used in this deployment.


For more information about server response delay configuration, see Connection-Control Plugin Installation.

Monitoring Failed Connection Attempts

Failed connection attempts can be monitored using these information sources:

To test the connection-control plugin and view monitoring data:

  1. Open a terminal and connect to the server as root:

    $> cd /usr/local/mysql 
    $> bin/mysql -u root -p
    Enter password: (enter the root password here)
  2. Open a second terminal and perform four connection attempts as root, specifying an incorrect password each time. There should be a small but noticeable delay on the fourth connection attempt.

    $> cd /usr/local/mysql 
    $> bin/mysql -u root -p
    Enter password: (enter incorrect password here)
  3. In the first terminal, issue this statement to view Connection_control_delay_generated status variable data. Connection attempts that exceed the connection_control_failed_connections_threshold threshold value of 3 are counted.

    mysql> SHOW STATUS LIKE 'Connection_control_delay_generated';
    | Variable_name                      | Value |
    | Connection_control_delay_generated | 1     |
  4. In the first terminal, issue this statement to view INFORMATION_SCHEMA.CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS data. All four failed connection attempts are counted.

    |               4 |