Threat Level: green Handler on Duty: Jan Kopriva

SANS ISC: UDP port 1900 DDoS traffic - SANS Internet Storm Center SANS ISC InfoSec Forums

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UDP port 1900 DDoS traffic

I guess this is my day for asking for feedback from our readers.  Again, I'm going to ask "Got packets?"  On 22 Aug, one of our readers (Paul) commented on the Port 1900 page that he was seeing a DDoS on port 1900, with packet sizes of 300 bytes.  This is a development we've been watching at $dayjob, too, but I was wondering if anyone (including Paul) has packets so we can try to figure out what the amplification mechanism might actually be (if you have the packets, please share via the contact page).  What we're seeing in Dshield data is a little odd and different from what I'm seeing at $dayjob.  You'll note below that there were a more targets until they suddenly dropped off on 18 Jun.  On the other hand, the sources seem to be trending upward (at least, peaking higher).  Unfortunately, we only have source and target counts in the Dshield data, not byte volumes.  Compare that with what we're seeing at the $dayjob as shown in the webcast we do weekly there (from 39:55 in this video -- watch to about 47:00 if you want to see our discussion of all the reflective DoS ports we're watching).


Jim Clausing, GIAC GSE #26
jclausing --at-- isc [dot] sans (dot) edu

I will be teaching next: Reverse-Engineering Malware: Malware Analysis Tools and Techniques - SANS DFIR Summit & Training 2022


423 Posts
ISC Handler
Aug 25th 2014
The only udp dst port 1900 traffic I have observed on our network since reading this post yesterday is upnp scanning related.

2 Posts
This "SSDP Amplification Scanner" could be related, see
Erik van Straten

129 Posts
Cool, I hadn't seen that tool before, I'll have to take a look. Thanx.

423 Posts
ISC Handler
This post is a little old, just saw one of these tonight. UDP 1900, 250 byte packets At its peak measured about 170Meg of traffic for a duration of about 5 minutes. Began promptly at 1730 on 21 May (PST). Claimed origination IPs were all over the place but mostly residential service, it appears, except for a few details of note. First packet came from Russia then began arriving from mostly US and Canada (according to the *claimed* IP address).
2 Posts
To follow up on my earlier, it was not 250 byte packets but it was 250 packets from each source IP of varying length. Exmaple snippet:

Date flow start Duration Proto Src IP Addr:Port Dst IP Addr:Port Out Pkt In Pkt Out Byte In Byte Flows
2015-05-21 17:32:25.217 0.000 UDP <-> x.x.x.x:59860 0 250 0 74250 1
2015-05-21 17:32:04.928 0.000 UDP <-> x.x.x.x:3718 0 250 0 87250 1
2015-05-21 17:33:29.050 0.000 UDP <-> x.x.x.x:59585 0 250 0 84500 1
2015-05-21 17:33:02.444 0.000 UDP <-> x.x.x.x:5262 0 250 0 90750 1
2015-05-21 17:31:56.313 0.000 UDP <-> x.x.x.x:42917 0 250 0 89500 1
2015-05-21 17:32:39.476 0.000 UDP <-> x.x.x.x:64858 0 250 0 81250 1
2015-05-21 17:33:00.749 0.000 UDP <-> x.x.x.x:51886 0 250 0 78500 1
2015-05-21 17:32:07.785 0.000 UDP <-> x.x.x.x:6433 0 250 0 83250 1

So the packets were of slightly varying size.
2 Posts
The origination IPs cannot be spoofed, those machines are the reflectors and you were the victim. The spoofed addresses were the ones going into the reflectors, and they were all spoofed to point to you so you would get the replies.

Any chance you have full packet capture? IF…


324 Posts
ISC Handler

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