[Snort-users] DNS Help/ SID 1948

Demetri Mouratis dmourati at ...3877...
Wed May 7 15:40:07 EDT 2003


Uhh,

Don't DNS zone transfers use TCP?

On Thu, 8 May 2003, Vanish Pattni (DSL AK) wrote:

> we get a few of these everyday. However, at first we checked the dns server
> logs to see if a zone transfer had indeed happened but that was not the
> case. Finally we settled down to the fact that udp is connectionless and the
> packets could easily be spoofed.
>
> TCP zone transfers have to come from a valid ip address and that is what you
> really have to look out for. Check your DNS server logs for any uncertainty.
>
> cheers
> Vanish
>
> -----Original Message-----
> From: Everist, Benjamin S. (NASWI) [mailto:EveristB at ...8190...]
> Sent: Thursday, May 08, 2003 6:45 AM
> To: snort-users at lists.sourceforge.net
> Subject: [Snort-users] DNS Help/ SID 1948
>
>
>
> Is the alert below really a DNS Zone transfer?  If not, what is it?
>
> ----------------------------------------------------------------------------
> --
> #(1 - 324871) [2003-05-06 09:15:04] [arachNIDS/212] [cve/CAN-1999-0532]
> [icat/CAN-1999-0532] [snort/1948]  DNS zone transfer UDP
>
> IPv4: 207.115.64.2 -> my.home.net
>       hlen=5 TOS=0 dlen=170 ID=0 flags=0 offset=0 TTL=47 chksum=51810
> UDP:  port=53 -> dport: 53 len=150
> Payload:  length = 142
>
> 000 : 54 50 80 00 00 01 00 00 00 02 00 03 03 31 31 36   TP...........116
> 010 : 06 31 31 32 2F 32 38 03 31 33 35 02 31 38 02 31   .112/28.135.18.1
> 020 : 32 07 69 6E 2D 61 64 64 72 04 61 72 70 61 00 00   2.in-addr.arpa..
> 030 : 0C 00 01 C0 10 00 02 00 01 **00 00 FC** DB 00 12 03   ................
>
> 040 : 6E 73 32 08 69 73 6F 6D 65 64 69 61 03 63 6F 6D   ns2.isomedia.com
> 050 : 00 C0 10 00 02 00 01 **00 00 FC** DB 00 06 03 6E 73   ..............ns
>
> 060 : 31 C0 43 C0 5D 00 01 00 01 00 00 2A 30 00 04 CF   1.C.]......*0...
> 070 : 73 40 02 C0 3F 00 01 00 01 00 00 2A 30 00 04 CF   s at ...846...?......*0...
> 080 : 73 40 03 00 00 29 10 00 00 00 80 00 00 00         s at ...979...)........
>
> and here's the sig that triggered it:
>
> alert udp $EXTERNAL_NET any -> $HOME_NET 53 (msg:"DNS zone transfer UDP";
> content: "|00 00 FC|"; offset:14; reference:cve,CAN-1999-0532;
> reference:arachnids,212; classtype:attempted-recon; sid:1948; rev:1;)
>
> Your thoughts are appreciated...
>
> v/r,
>
> Benjamin Everist
>
>

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Demetri Mouratis
dmourati at ...3878...





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