[AusNOG] VoIP Hack Attempts

[Tom.Minchin at csiro.au]

We've had similar attacks in the past (attacking our video conferencing units) - one option if you have any kind of IPS or deep packet inspector in front is to drop the SIP registration requests as they all seem to have the same client name. From my research (Google) they use a specific client name which is not used by legitimate requests.

However, I'm sure version 1.1 of their scanner will fix that...

Tom

From: Skeeve Stevens [mailto:Skeeve at eintellego.net]
Sent: Monday, September 27, 2010 10:13 PM
To: ausnog at ausnog.net List <ausnog at ausnog.net>
Subject: [AusNOG] VoIP Hack Attempts

Hey all,

I’ve got a few customers who have noticed a large recent jump in SIP scans against their networks.

Null routing helps the response but doesn’t stop the registration initiation – loading up servers with registrations.

This is easy to stop on closed VoIP systems, but not on hosted Voice platforms which users come from other ISP’s/networks, this seems to be very difficult.

Does anyone have any ideas – we are fresh out at the moment, apart from beefing up security on the VoIP servers themselves using fail2ban or other things that detect rapid registrations and then firewalls them.

Having a normal server hacked is one thing but VoIP hacking has taken on a new intensity as the hackers can make a LARGE amount of money by comprising a VoIP system.

Recently, we’ve been brought in to clean up the mess in several incidents where a couple of VoIP systems have been compromised in incidents totalling over AU$100,000.

And the carriers are rarely sympathetic.

If it isn’t obvious as to how/why they’re doing this – the hackers get in, open a SIP account so their VoIP system can register, and then they channel certain calls via the comprised system.  This has the effect of them charging the end user and making money, while not paying for the calls to be delivered to the destination.

Advice:

-          Block destinations to obscure places that your customers are unlikely to call, and only unblock them if they request

-          Watch billing to certain locations and if there is a massive jump, do something

-          Watch your customers and if their billing jumps by a massive amount, alert them as fast as you can – or you just might be liable

...Skeeve

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Skeeve Stevens, CEO
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