SNMP: The next big thing in DDoS Attacks?
It started with DNS: Simple short DNS queries are easily spoofed and the replies can be much larger then the request, leading to an amplification of the attack by orders of magnitude. Next came NTP. Same game, different actors: NTP's "monlist" feature allows for small requests (again: UDP, so trivially spoofed) and large responses.
Today, we received a packet capture from a reader showing yet another reflective DDoS mode: SNMP. The "reflector" in this case stands nicely in line for our "Internet of Things" theme. It was a video conferencing system. Firewalling these systems is often not practical as video conferencing systems do use a variety of UDP ports for video and audio streams which are dynamically negotiated. As a result, they are often left "wide open" . And of course, these systems not only let attackers spy on your meeting rooms, but the also make great SNMP reflectors as it turns out.
Here is an anonymized traffic capture (target anonymized with 192.0.2.1):
117.27.239.158 -> 192.0.2.1 SNMP 87 getBulkRequest 1.3.6.1.2.1.4.21.1.1
192.0.2.1 -> 117.27.239.158 IPv4 1514 Fragmented IP protocol (proto=UDP 17, off=0, ID=1f48)
192.0.2.1 -> 117.27.239.158 IPv4 1514 Fragmented IP protocol (proto=UDP 17, off=1480, ID=1f48)
... [ additional fragments omitted ] ...
192.0.2.1 -> 117.27.239.158 IPv4 1514 Fragmented IP protocol (proto=UDP 17, off=54760, ID=1f48)
192.0.2.1 -> 117.27.239.158 IPv4 1514 Fragmented IP protocol (proto=UDP 17, off=56240, ID=1f48)
192.0.2.1 -> 117.27.239.158 SNMP 664 get-response [... large response payload ...]
That is right! A simple 87 byte "getBulkRequest" leads to about 60k Bytes of fragmented data being sent back. We can only assume that poor 117.27.229.158 is the victim of this DoS attack. The user reporting this saw about 5 MBit/sec of traffic.
Similar to what we have seen with other reflective attacks like this, the fragmentation of the traffic is likely going to make filtering even harder. Prolexic posted a white paper about some of the different DrDOS attacks, including SNMP attacks [1]
So what to do:
- SNMP should probably not traverse your perimeter. Stop it at the firewall. (and I don't think video conferencing systems need it)
- proper egress/ingress control is a good idea. But you already knew that.
[1] http://www.prolexic.com/kcresources/white-paper/white-paper-snmp-ntp-chargen-reflection-attacks-drdos/An_Analysis_of_DrDoS_SNMP-NTP-CHARGEN_Reflection_Attacks_White_Paper_A4_042913.pdf
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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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| Network Monitoring and Threat Detection In-Depth | Singapore | Nov 18th - Nov 23rd 2024 |
Comments
The SNMP reflection DDoSes have been going on for longer. Saw them 4 to 5 months before the first NTP MONLIST reflections.
My impression was the SNMP reflections disappeared or became less predominant after NTP MONLIST came out.
Perhaps bad guys concentrating their efforts on the more abusable issue.
Now when people start patching their NTP servers; a bunch of bad guys revert back to SNMP and DNS reflection, perhaps.
Anonymous
May 8th 2014
1 decade ago
Anonymous
May 8th 2014
1 decade ago
Anonymous
May 9th 2014
1 decade ago
In the late 1990s, the Smurf attack was a quite popular reflection/amplification vector, until Cisco and other router manufacturers made 'no ip unreachables' a configuration default.
DNS reflection/amplification attacks were first posited around 2000 or 2001, and started to show up in the wild in late 2004/early 2005.
SNMP reflection/amplification attacks began showing up in the wild in the 2006 - 2007 timeframe.
ntp reflection/amplification attacks began showing up in the wild around 2008 - 2009.
chargen reflection/amplification attacks began showing up in the wild around 2009 - 2010.
tftp reflection/amplification attacks began showing up in the wild around 2009 - 2010.
None of this stuff is new.
Anonymous
May 9th 2014
1 decade ago
Anonymous
May 9th 2014
1 decade ago
The public brouhaha over ntp reflection/amplification attacks began when some gamer script-kiddies (there's always been a strong correlation between online gaming and DDoS attacks) got hold of some simple scripts which had filtered downwards from more sophisticated attackers, along with access to compromised servers on IDC hosting networks which didn't enforce anti-spoofing.
They attacked online game services with very large ntp reflection/amplification attacks; these services typically have tens of millions of simultaneous users, and that's what brought this attack methodology into the view of non-specialists.
But there are DDoS attacks using all these various reflection/amplification methodologies taking place every second of every minute of every our of every day of every year. Attackers add new methodologies to their individual arsenals, but we don't see DNS reflection/amplification attacks being *discarded* in favor of ntp reflection/amplification attacks, for example.
Anonymous
May 9th 2014
1 decade ago
The one thing which would make all forms of reflection/amplification attacks impossible is anti-spoofing at all network edges. BCP38/84 is the answer.
Anonymous
May 9th 2014
1 decade ago
Anonymous
May 9th 2014
1 decade ago