disable NULL BIND on your LDAP server

From: Doug Fox (dfox138-no-spam_at_hotmail.com)
Date: 10/17/05 

Date: Mon, 17 Oct 2005 11:39:07 -0400

Used NESSUS scanned a server. It issued a warning saying that "ldap
(389/tcp) - improperly configured LDAP servers will allow any user to
connect to the server and query for information. The solution is to
"disable NULL BIND on your LDAP server."

Did google many times, search results only show the
"suggestion/recommendation", but none of them show the steps to disable it.

Could someone please point me to a place where I can obtain the steps.

Thanks,