From: "Len L." <len@euler.com>
To: netfilter@lists.netfilter.org
Cc: "Len L." <len@euler.com>
Subject: Blocking access to UDP port 53 (DNS)
Date: Mon, 11 Aug 2003 11:25:21 -0500 [thread overview]
Message-ID: <12CC60849165134FB7DF8570B621F4D5FC4C@mailxserver.euler.com> (raw)
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Does anyone know how to block the use of a DNS server (udp port 53) from outside, but still have external mail be able to resolve addresses?
Here is what I tried ( xxx.xxx.xxx.0 is our external net that the dns server is on)
iptables -A INPUT -s xxx.xxx.xxx.0/24 -p udp -j LOG --log-prefix "XXX LOCAL UDP DNS XXX "
iptables -A INPUT -s xxx.xxx.xxx.0/24 -p udp -j ACCEPT
iptables -A INPUT -p udp -j LOG --log-prefix "XXX INPUT UDP LOG-drop XXX "
iptables -A INPUT -p udp -j DROP
DNS requests from our machines works with the rules above, but here is the message a remote system gets when someone mails us:
Aug 11 10:33:52 remotemachine sendmail[16732]: h7BFVAAR016730: to=<len@machine.ourdomain.com>, ctladdr=<someone@their.domain.com> (0/0), delay=00:01:49, xdelay=00:01:49, mailer=esmtp, pri=30344, relay=machine.ourdomain.com., dsn=4.0.0, stat=Deferred: Name server: machine.ourdomain.com.: host name lookup failure
Len Laulainen
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next reply other threads:[~2003-08-11 16:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-11 16:25 Len L. [this message]
2003-08-11 17:02 ` Blocking access to UDP port 53 (DNS) Ramin Dousti
-- strict thread matches above, loose matches on Subject: below --
2003-08-11 16:50 Josh.Berry
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