Snort mailing list archives

RE: Can I stop these port 53 detects?


From: "Erik Norman" <erik.norman () ccnox com>
Date: Wed, 27 Jun 2001 15:57:23 +0200

It is with interest i read this thread, as i am experiencing the same
problem.

In my local.rules file, which btw is not commented out in snort.conf, i have
entered

        pass tcp <a certain ip> 53 -> <our dns> 53
        pass udp <a certain ip> 53 -> <our dns> 53


Snort have been completely restarted, without errors.

I am using standard Snort 1.7 on RH6.2.


I still receive entries like this:

Jun 27 15:32:20 localhost snort[32395]: MISC source port 53 to <1024: <a
specific ip>:53 -> <our dns>:53


Are the pass-rules entered above correct? Is 'pass' working satisfacory in
1.7? Why is the sky blue?

Regards
Erik

-----Original Message-----
From: snort-users-admin () lists sourceforge net
[mailto:snort-users-admin () lists sourceforge net]On Behalf Of Phil Wood
Sent: den 22 juni 2001 01:44
To: info.sec () att net
Cc: snort-users () lists sourceforge net
Subject: Re: [Snort-users] Can I stop these port 53 detects?


On Thu, Jun 21, 2001 at 10:20:14PM +0000, info.sec () att net wrote:
Thanks for the feedback!

I tried this (in local.rules):

pass tcp dns.server.ip.address 53 -> $HOME_NET any
(msg: "no problem";)

(That's all one line.  My e-mail client may have wrapped
it.)

Then I killed Snort and restarted with the -o option.
I still get a log full of alerts.  [SIGH]

Did you also fix the rules that think that :1024 means < 1024, when
they should have :1023 which means <= 1023 which is the same as < 1024.
Did I make myself clear.  %^)



You need some pass rules for 53 -> 53.  And you need to fix the
<1024 rule.  It probably has a :1024 in it.  That catches legitimate
dns of the form 1024 -> 53.  Change it to :1023.

On Thu, Jun 21, 2001 at 08:06:09PM +0000, info.sec () att net wrote:
Greetings,

I hope this isn't in a FAQ somewhere - I couldn't find
it.

I'm running Snort 1.7 on an OpenBSD 2.8 system.
I have a line in my snort.conf file like this:

# Define the addresses of DNS servers and other hosts
var DNS_SERVERS [aa.bb.cc.dd/32,ee.ff.gg.hh/32]


But my alert log still fills up with these:

[**] MISC source port 53 to <1024 [**]
06/21-12:55:52.409466 ee.ff.gg.hh:53 -> 1.2.3.4:685
UDP TTL:246 TOS:0x0 ID:35418 IpLen:20 DgmLen:205 DF
Len: 185

Where 1.2.3.4 is the outside interface of my firewall.

Is there anything I can do to stop Snort from keying on
these port 53 packets from one of our DNS servers?

TIA!

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--
Phil Wood, cpw () lanl gov


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--
Phil Wood, cpw () lanl gov


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