Re: Protocol 17 floods from Vietnam & Mexico?

[Christopher Morrow <morrowc.lists () gmail com>]

On Wed, Sep 13, 2017 at 9:59 AM, Krunal Shah <KShah () primustel ca> wrote:

> It might be spoofed source IPs
if you are seeing large fragmented udp packets.. it's almost always not
spoofed.
or historically speaking anyway it's not been spoofed.

There are cases with dns reflection that include spoofing, but by the time
you see the large packet .. that's not spoofed it's coming from the dns
server talking to you, why it's talking to you is due to spoofing, but
that's outside (most times) your span of control.


> Krunal Shah
>
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>
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> -----Original Message-----
> From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Mark Andrews
> Sent: Tuesday, September 12, 2017 10:45 PM
> To: Large Hadron Collider
> Cc: nanog () nanog org
> Subject: Re: Protocol 17 floods from Vietnam & Mexico?
>
>
> In message <08ed2903-c81c-aa2e-cd04-4fa117840d14 () gmx com>, Large Hadron
> Collider writes:
> > Yes, I'm being UDP flooded. I worked that out by grepping /etc/protocols.
> >
> >
> > On 12/09/2017 18:24, Matt Harris wrote:
> > > Protocol 17 is UDP.  UDP is pretty common on the internet. Not sure
> > > why source and destination ports aren't being shown by your tool
> > > there, might be malformed UDP packets designed to obscure themselves
> > > from or otherwise evade some intrusion detection or firewall systems.
>
> No ports are listed because they are not the initial fragment of the UDP
> packet.  Only the initial fragment that contains the UDP header has the
> ports reported.
>
> Mark
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: marka () isc org
>
>
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