How to block toad pl/sql code

CREATE OR REPLACE TRIGGER block_toad
AFTER LOGON
ON DATABASE
DECLARE
--Declare a cursor to find out the program
--the user is connecting with.
CURSOR user_prog IS
SELECT program FROM v$session
WHERE audsid=sys_context('USERENV','SESSIONID');
--Assign the cursor to a PL/SQL record.
user_rec user_prog%ROWTYPE;
BEGIN
OPEN user_prog;
FETCH user_prog INTO user_rec;
IF user_rec.program IN ('TOAD.exe')
THEN
RAISE_APPLICATION_ERROR(-20001, 'You are not allowed to login with TOAD');
END IF;
CLOSE user_prog;
END;