protecting network from external attack (SQL server 2012 bruteforce) My SQL server 2012 log indicates multiple bruteforce attempts to logon to the server. 

Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: xxx.xx.xx.xx]

The account has a very secure password, which buys time for now.

It was recommended that I use a trigger to prevent ip logins. However, this is proving ineffective. How do I put an end to this issue.

CREATE TRIGGER IPtrigger
    ON ALL SERVER
    FOR LOGON
AS
BEGIN
    DECLARE @IP Varchar( 500 )
    SET @IP = EVENTDATA().value( '(/EVENT_INSTANCE/ClientHost)[1]', 'varchar(500)' )

    -- set of the restricted IP addresses
    IF @IP IN ( 'xxx.xx.xx.xx' )
    BEGIN
        Print 'IP BANNED FROM LOGON: ' + @IP
        ROLLBACK TRANSACTION
    END
END
GO
You can disable SA account and wait until attack ends. This is not a solution for the problem, but can buy some time to reconfigure your network.

/* Disable SA Login */
ALTER LOGIN [sa] DISABLE
 GO
/* Enable SA Login */
ALTER LOGIN [sa] ENABLE
 GO