One of the steps you can take to stop spam scripts is to enable SMTP Restrictions in WHM. This particular feature will prevent users from bypassing the mail server to send mail. When enabled it only allows delivery through MTA, mailman, and root connect to remote SMTP servers.
NOTE: This setting does require that you have root access to WHM
Using SMTP Restrictions
You can also click on Tweak Settings and use the Mail section to make further changes to the configuration.