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Dear support personnel

We have repeatedly been scanned for open SIP (VoIP) access from IP
adresses: 113.105.152.101, 113.105.152.102 and 113.105.152.104.
The last time was February 27th 2010, but this scanning has been going
on for a long time, first reported back in December 2009.

http://www.usken.no/2010/02/and-the-scanning-just-keeps-on-coming/

http://pbxinaflash.com/forum/showthread.php?t=6223

http://www.freepbx.org/forum/freepbx/users/call-log-with-asterisk-in-both-source-and-clid-columns

We believe this is fraudulent activity to scan for open SIP gateways to
route traffic towards the telephony network.

Please inform the owners of these servers that this activity is not
tolerated and seen as an attack on our servers.

regards

sjur

One guy with an Asterisk got hit December 2009 and others back in November. Others starts debugging and asks what it is in public support forums. There will be even more of this scanning coming next months!

Some has added firewall rules like:

deny 113.105.152.102/255.255.255.255
deny 66.117.50.225/255.255.255.255
deny 204.57.122.6/255.255.255.255

But this will not last long until some new IP addresses show up.

What to do about it?

Secure your IP PBX and don’t let port 5060 be open for everybody.
If you must, have very long and strong passwords on all extensions. (or use port knocking..)
Make sure that callers into your PBX is not allowed onto any Outbond context making you pay their calls…

Dan York has a good overview of it on his blog:

Updating a story we have literally been following for years ever since it broke back in July 2006, the FBI recently issued a news release indicating that Edwin Pena pled guilty in what we have been calling the “Pena/Moore VoIP fraud case”. From the news release:

Edwin Pena, 27, a Venezuelan citizen, pleaded guilty before U.S. District Judge Susan D. Wigenton to one count of conspiracy to commit computer hacking and wire fraud and one count of wire fraud. Judge Wigenton continued Pena’s detention without bond pending his sentencing, which is scheduled for May 14.

What made it interesting for Sandro in EnableSecurity was that most traffic was UDP (60 %) and almost 90 % to IP addresss 1.1.1.1. This is a text from RIPEs article about it:

We found that almost 60% of the UDP packets are sent towards the IP address 1.1.1.1 on port 15206 which makes up the largest amount of packets seen by our RRC. Most of these packets start their data section with 0×80, 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 1.1.1.1 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 1.1.1.1. 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 1.1.1.0/24 and 1.2.3.0/24 on 2 February 2010.

An affected user may unintentionally execute scripts or actions written by
an attacker. In addition, an attacker may obtain authorization cookies
that would allow him to gain unauthorized access to the application.

This is just the beginning of vulnerabilities in different VoIP applications. Up until now, there has not been the need of vulnerabilities to exploit VoIP services. Too many IP PBXes has been configured insecure, and easy to abuse.

The next wave will see more exploits beeing used towards IP PBXes. They are often based on same protocols and applications as any other server….

Do you want to learn more about investigating attacks?

Here is your challenge!

The Honeynet Project has released this years first Scan of the Month challenge! It has many levels and now you can test if you are up to it!

If he really need his Asterisk available on port 5060, he could use SSH tunneling for the SIP signalling or a port knocking method to open port 5060 from his current IP when needed.

Will check what he does on the next attack.

Have you checked your logs lately?

How they do it:

1. They use SIPVicious to scan with SIP OPTIONS messages.
2. If they get a response, this scan followed up with SIP REGISTER on all extensions from 100 to 9999
3. Then they pick an EXTENSION and do brute force password on it. (another load of REGISTER)

What does this have to do to you?

If you have a VoIP platform which handles REGISTER or INVITES on a public IP, you BETTER have good passwords! And you need to handle large loads if have no protection!

If you can lock it down based on access lists or with VPN, do so now!

Great work and I’m looking forward to test it out live!

Scannings on port 5060 has exploded the lastest days. Previously it was a couple hits in the week, now it’s up to a 100 a day. This means that if your VoIP setup is not 100% secure, others will find it and abuse it!And you will get the telephony bill!

Get to it, secure your VoIP communication platform right now!

Check the following:

• All users has strong passwords
• Access Lists are updated and preferably both ways (both incoming and outgoing traffic on the server)
• No unused services are enabled
• Latest patches are on the server OS
• Latest patches are on the application
• Latest SECURE firmware on the hardware endpoints (phones etc.)
• Other services on the plattform like Web servers, TFTP, FTP, SSH are locked down or VERY strong passwords
• Encrypt the traffic from the user and into the server (to make eavesdropping harder)
• Make the PCs accessing your platform secure. Any keycatchers or sniffers installed here?
• Forgotten someting? Please comment