Safe to put a Linksys 3000 in a DMZ

What exactly would anyone be able to hack in an ATA..?

Ivor

Well, you could attach to it and make outgoing phone calls on Dave's dime...

EXACTLY what I was thinking someone hacking there way in and taking my details and using my account ..... Not sure how vulnerable a ATA is, also maybe possible to hack back into the network via the ATA....??

Dave..

I can't see how.

Ivor

Well, it's got an FXO port, which Dave has attached to his incoming POTS line. If I can get at it, I can make calls (including long distance calls and $500/min 900 calls, which I've previously arranged to get a cut of) on Dave's POTS line.

I can see what you're getting at, but I can't see how you would achieve it. In almost 2 years of using VoIP on a day to day basis I have never heard of an ATA being "hacked" in the manner you describe. An ATA isn't the same thing as a PC. I am prepared to be proven wrong, but it's not something I have ever heard of happening, or even discussed before now.

Ivor

Ivor, that's a dangerous assumption to be made really. You're trusting that there's NO possible way that Sipura has a security hole. Regardless of the fact that it doesn't run a traditional OS, it has an embedded operating system of sorts and devices like this have security flaws as well. Just because it hasn't happened yet doesn't mean it won't happen, remember when (if you've used the internet long enough you well) the internet was "safe" and no one got hacked, was this because none of the systems had security problems? No, security was laughable, it was just the fact that there were a lot less monkeys out there with a desire to do such things. Once something becomes more interesting and widespread (and VoIP has already become this) it is a huge target of interest to be hacked. One very obvious problem with the Sipura is the access to the web interface doesn't even support SSL! When it comes to security it's better not to make assumptions and be overly paranoid than to be overly sloppy and find out later you were wrong. I believe that, even behind some type of security device, SIP devices are still going to have exploits exposed.

Imagine you're on an extended trip, halfway around the world, using your SPA-3000 for communication and it's hooked onto the local phone line so you can make outgoing local calls as well. Now, you've left it in the DMZ and it gets hacked. What are you going to do? Call and cancel your phone line it's connected to in order to mitigate the damages?

Ok, but let me hear of an actual *documented* case where it has happened before I get paranoid.

Many systems, SIP included, by their very nature have to be seen by the outside world in order to work. Even if they're not in the DMZ (they're not here), are my ATA's going to be hacked..?

Ivor

What is the alternative if one wants to use the VoIP number for *inbound* calls? Just like any other Internet node, you have to keep your ATA firmware updated to the latest version.

It would be nice if the device manufacturers and service providers can provide a "security announcement" list for such updates.

If you are going to use the device for outbound calls only then you can place the ATA behind a firewall and it should work.

-- Arun Khan

One can probably close most ports leaving only the ones needed for normal operation open.

sip/udp rtp/udp domain/udp (eg. named/bind) domain/tcp (ditto, needed also) ntp/udp (time)

If the ATA is multi-call capable, one might also keep a handful of consecutive udp ports open for use by rtp and tell the ATA to use those instead of the traditional single port assigned to rtp.

Clearly one also wants to avoid any NAT translation and assign all SIP endpoints genuine routable addresses.

-wolfgang