Your external DNS should not be a secondary of your internal server. It should be a separate DNS with only the informations about your DMZ servers and MX record.
You should work in split DNS mode. Your internal DNS have the informations about the internal AND DMZ server. Your DMZ DNS only know about your DMZ server. Why your DMZ need access to the root DNS? Because your mail server need to know what my e-mail server address is.... -----Message d'origine----- De : Michael Vaughan [mailto:list@;predator-hunter.com] Envoyé : 4 novembre, 2002 15:50 À : 'Naman Latif'; 'security-basics' Objet : RE: Securing DNS Server -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Folks, If I am not mistaken, the DNS server in the DMZ should be a SECONDARY IE: a non-writable database. Furthermore, the DNS server on your internal network should be the primary giving ONLY appropriate information regarding the location of external services. IE: not allowing DNS zone transfers except from specific servers...etc. Essentially, the external DMZ server services external requests for resolving services offered in the DMZ ONLY and the internal DNS server (Primary) offers services to internal clients for resolving outside sites & services. My question is why would you be allowing ANY outgoing connections from your DMZ DNS server to external root servers other than what is on your site? If you have other services located at other locations...you can add those to the DNS manually or through zone transfer. I would propose that the DMZ DNS server should ONLY resolve your DMZ services and no one else's. IE: Why would I want someone using my DNS server externally to resolve yahoo? Basically I am saying that if the service can not be resolved externally to your site(s) then it should fail. Your internal DNS server would service all of your internal clients and would not be accessible from external sources period. There are notable exceptions depending on your requirements but am I missing the point of your question? I am assuming you have a DMZ and you are in NO WAY allowing anyone to connect to your internal network directly. Is that correct? - -Michael Vaughan [EMAIL PROTECTED] http://www.predator-hunter.com The information contained in this message may contain privileged and confidential information and is intended only for the internal company use of the individual or entity named above. If the reader of this message is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any examination, distribution or copying of this communication is strictly prohibited. Furthermore, any and all recipients of this message are prohibited from engaging in the unauthorized dissemination of the information contained herein to person(s) outside the company. If you have received this communication in error, please notify sender immediately. - -----Original Message----- From: Naman Latif [mailto:naman.latif@;inamed.com] Sent: Friday, November 01, 2002 7:31 PM To: security-basics Subject: Securing DNS Server Hi, I am trying to restrict Access to our DNS Server from Outside using a Cisco IOS Firewall. Initially we only had Port 53 Access to this Server from outside. But it turned out that when our DNS Server has to query a root name server, it sends out a UDP query with a random higher (>1023) source port number, which means that I will have to open >1023 Ports access to this server from outside. In this situtation How do I protect my DNS server from outside attacks on higher port numbers ? Is there a range of Source Port numbers that a BIND DNS server would use, when querying outside servers ? -----BEGIN PGP SIGNATURE----- Version: PGP 7.0.4 iQA/AwUBPcbdZuqV6OTyHFF7EQJoPgCgxyxV0964WY3BFQAuj6VxxzXpZ3QAoKNc zjic3/Q9TAzAe8FYYqGSt66i =oLS0 -----END PGP SIGNATURE-----
