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>I'm using Shorewall 4.0.6 on a Debian Etch server with kernel 2.6.24.
>The server is running asterisk 1.6 with few IP Phones registered to the
>asterisk, on the internal Interface eth0. The server has indeed a public
>interface eth1 used by asterisk to connect to external SIP providers.
>Now, I simply can't prevent an external IP Phone from registering on my
>asterisk on interface eth1.
>I tried to stop the UDP traffic with this rule (rules file):
>DROP net:XX.XX.XX.XX fw udp 1024:65535
>Where XX.XX.XX.XX is the public ip addres of the IP Phone. How could it be?
>The interface file looks like:
>net eth1 detect tcpflags,nosmurfs
>loc eth0 detect tcpflags,nosmurfs
>The policy file looks like:
>$FW all ACCEPT
>net $FW DROP info
>net loc DROP info
>net all DROP info
>all all REJECT info
Firstly, you only need to block port 5060 to stop SIP (assuming you
aren't running a non-standard port). Also be aware that SIP can use
TCP as well as UDP.
But I see that your policies will drop the traffic anyway, so a drop
rule is redundant.
As Tom has already pointed out, if the phone had a connection active
before you invoked the firewall then that connection will remain
open. Also check your rules file for anything that might be
explicitly permitting the traffic.
Lastly, check that you don't have anything configured on your
Asterisk setup that might be sending outbound SIP packets to the
device - that would be enough to create an open connection which
would permit inbound traffic as well.
Not related to this, but make sure you use good strong passwords for
your devices. We have to allow external access to our system at work
to cater for home and mobile users - we regularly get brute force
attacks, one day we had two separate attacks that overlapped !
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