[asterisk-users] asterisk security....again

[Terry Brummell]

When he says "customers" I am assuming he means remote customers.  It
sounds like he is a reseller of telecom facilities to me.  Which means
his customers most likely have ATA's with port 5060 forwarded to the
ATA, or they are direct on the I'net.

He has already set the ATA to only allow calls from the proxy server, so
sounds like he has plugged the hole.

 

They are not 'sniffing' your traffic, they are guessing/scanning.
That's it, that's all, no great conspiracy going on.  They look for open
5060, then send SIP requests to it hopefully finding a badly implemented
SIP solution to which they can dial through.  Once they determine they
cannot get through, the script will move on to the next sucker.

 

You have a couple of options, which you could implement at *each* of
your customers if you wanted.  Set up a VPN, tunnel the SIP/RTP traffic
through it.  Set up IPTables at the customer to only allow SIP from your
IP.  Or, do what you have already done and forget about these idiots
doing the scan, they are harmless at this point.

 

Vlans and DMZ for the server do no good as the attacks are being
directed at the remote client side, not the server.

 

 

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Ricardo
Carvalho
Sent: Monday, February 28, 2011 6:31 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] asterisk security....again

 

Probably, you are receiving INVITE attacks from some tool like
sipvicious. You should rearange your network to cover some inportant
security issues.

 

The IP address of you server can be revealed in some unincrypted SIP
signaling of some call through the Internet to/from your server's
client, or simply by your client SRV record in the DNS, if you added it
to his DNS.

 

Probably your network is exposed to the Internet. To address those
situations, you can use a distinct VLAN to address SIP phones and you
also can use port security at the switching ports where you connect your
ATAs and phones. You should also deliver with tagging (802.1Q) that VLAN
to those ATAs and phones. This should protect you from inside sniffers.

This VLAN should just communicate with the DMZ where you should have
your asterisk server and between those two networks you should only open
the needed ports - for a common SIP infrastructure you should open UDP
5060 and the specified UDP range shown in rtp.conf file for the media to
pass. Phones VLAN should not communicate directlly with the world, just
in the outbound direction if you like. 

 

Regards,

Ricardo Carvalho.

 

 

 

 

 

On Mon, Feb 28, 2011 at 10:33 AM, Rizwan Hisham <rizwanhasham at gmail.com>
wrote:

Hi all,
The problem I have been experiencing since last month is that some of my
customers are getting calls with "Asterisk <Unknown>" caller id. Most of
them in the middle of the night. And my asterisk server has no record of
these calls. The customers were getting irritated as you can imagine. I
guessed the only way to receive incoming calls by by-passing the
registration server is thru sip-uri calls directly to customers. I have
updated the customers atas to not accept any calls from sources other
than the registration server. Thats all fine now. But the question is
how can anyone know the direct sip uri addresses of our customers.

My guess is that someone has been sniffing my server's sip traffic. In
that case what should i do to get rid of the sniffers?

If you think there is another reason for that then please tell me even
if you dont have the solution.

Thanks

-- 

Best Ragards

Rizwan Qureshi

VoIP/Asterisk Engineer

Axvoice Inc.

V: +92 (0) 3333 6767 26

E: rizwanhasham at gmail.com

W: www.axvoice.com <http://www.axvoice.com/> 





 

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