SIP scanning causes DDoS on IP 126.96.36.199
February 4, 2010
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RIPE said a long time ago that IPv4 is running out of addresses. Now they are also allocating the 1.x.x.x network for production traffic. But this is a bit problematic, since people have been using IP addresses like 188.8.131.52 and 184.108.40.206 as examples in scripts, tools and manuals. People who don’t know any better, they try contact these. When they routes to these networks where alive, a LOT of traffic started coming in.
What made it interesting for Sandro in EnableSecurity was that most traffic was UDP (60 %) and almost 90 % to IP addresss 220.127.116.11. This is a text from RIPEs article about it:
We found that almost 60% of the UDP packets are sent towards the IP address 18.104.22.168 on port 15206 which makes up the largest amount of packets seen by our RRC. Most of these packets start their data section with 0x80, continue with seemingly random data and are padded to 172 bytes with an (again seemingly random) 2 byte value.
This can actually be RTP traffic (VoIP audio traffic) generated from hosts that are vulnerable to SIP INVITE attacks, as Sandro points out in his comment and on his blog.
This is also alarming! This scanning with default RTP audio to IP 22.214.171.124 and port 15206 seems to be doing REALLY well on the Internet. There are a lot of VoIP unsecure platforms accepting and responding to ANY SIP INVITE they get. The software doing it is NOT SIPVicious, but another. It normally uses port 3058 to send the SIP INVITES from. If anybody knows something about this software, please contact me.
I have had a slide in my VoIP presentations about this scenario. If you do a SIP INVITE sweep, you should NOT have a valid IP address for the audio. Every successful INVITE would then generate at least 20 seconds of 0,1Mbit per second stream (g711 audio) to your IP address. Your SIP INVITE sweep with your IP as receiver for RTP traffic will not take long before it backfires on you and you get a DDoS on yourself (well earned though IMHO).
So what is next?
I would love to have a honeypot or get access to the traffic going to port 126.96.36.199. All hosts that would send RTP traffic to this address, should be contacted and asked to secure their servers!
Status now from RIPE:
Since the traffic patterns seemed to be stable we decided to withdraw the announcement of 188.8.131.52/24 and 184.108.40.206/24 on 2 February 2010.