It might be spoofed source IPs Krunal Shah -----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 -------------------------------- This electronic message contains information from Primus Management ULC ("PRIMUS") , which may be legally privileged and confidential. The information is intended to be for the use of the individual(s) or entity named above. If you are not the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this information is prohibited. If you have received this electronic message in error, please notify us by telephone or e-mail (to the number or address above) immediately. Any views, opinions or advice expressed in this electronic message are not necessarily the views, opinions or advice of PRIMUS. It is the responsibility of the recipient to ensure that any attachments are virus free and PRIMUS bears no responsibility for any loss or damage arising in any way from the use thereof.The term "PRIMUS" includes its affiliates. -------------------------------- Pour la version en français de ce message, veuillez voir http://www.primustel.ca/fr/legal/cs.htm

The port info is in the first  fragmented packet as was mentioned elsewhere.  My guess is someone fragmenting large packets ( the mtu is set to  1464 or so). and  the host is receiving those fragment, but it not  reconstructing the packets.  If  it is possible to do a tcpdump/wireshark etc , then the content of the packets can be very easily observed .   18:04:32.391082 IP 138-122-97-251.internet.static.ientc.mx >  umbrellix.net: ip-proto-17 18:04:32.391088 IP 138-122-97-251.internet.static.ientc.mx >  umbrellix.net: ip-proto-17 18:04:32.391110 IP 115.75.50.106.35180 > umbrellix.net.10454: UDP, bad  length 65500 > 1464 18:04:32.391145 IP 115.75.50.106 > umbrellix.net: ip-proto-17 18:04:32.391152 IP 115.75.50.106 > umbrellix.net: ip-proto-17 18:04:32.391158 IP 115.75.50.106 > umbrellix.net: ip-proto-17 From: Christopher Morrow <morrowc.lists@gmail.com> To: Krunal Shah <KShah@primustel.ca> Cc: "nanog@nanog.org" <nanog@nanog.org> Sent: Wednesday, September 13, 2017 7:59 AM Subject: Re: Protocol 17 floods from Vietnam & Mexico? 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

-----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

-------------------------------- This electronic message contains information from Primus Management ULC ("PRIMUS") , which may be legally privileged and confidential. The information is intended to be for the use of the individual(s) or entity named above. If you are not the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this information is prohibited. If you have received this electronic message in error, please notify us by telephone or e-mail (to the number or address above) immediately. Any views, opinions or advice expressed in this electronic message are not necessarily the views, opinions or advice of PRIMUS. It is the responsibility of the recipient to ensure that any attachments are virus free and PRIMUS bears no responsibility for any loss or damage arising in any way from the use thereof.The term "PRIMUS" includes its affiliates. -------------------------------- Pour la version en français de ce message, veuillez voir http://www.primustel.ca/fr/legal/cs.htm