Sjur Usken

Views on new technologies and business opportunities from Sjur Usken

Tag Archives: abuse

VoIP Abuse project – block the scanners


People has gotten tired of the VoIP scannings. Sometimes they manage to abuse the PBX or just fill up the logs with all the attempts. So Mr. Oquendo started on a list of IP addresses and networks that should be blocked.

The VoIP Abuse Project is aimed at minimizing abuse for networks that have publicly accessible PBX’s. As a security engineer at a managed service provider, one of our services is VoIP. Throughout the course of the day, I got tired of seeing VoIP based brute force attempts that I decided to out companies who sit around and choose to do nothing about the attacks coming from their networks. As a courtesy I often take the time out of my work day to write constant emails to abuse and security desks which go nowhere.

The link: http://www.infiltrated.net/voipabuse/

Personally I think companies should have a white list, just enabling the IPs that you really need to allow traffic from, but that is not easy if you are a VoIP provider with clients all over the world.

Next step on this list would be to automate the whole process.

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Another VoIP hacking in Norway


The latest month of scanning has seemed valuable for the hackers. A Norwegian municipality has been hacked and their PBX has been calling Somalia and a lot of others destinations we have picked up on our VoIP honeypots during the last month.

If you have an unsecure IP PBX on the net, now it will only take hours before it will be detected. Most normal cause for this is misconfiguration. The people setting up the IP PBX has not taken security seriously and the IP PBX is wide open for calling.

The simplest ways is that inbound calls is routed out again if no local destination is found.  A little harder is to just brute-force the password on extensions. I can only say, there will be more like this!

Norwegian version

English version

The hacker can sell this “gateway” to a third party dealing with calling cards. I have investigated frauds in Norway where they managed to send 1,2 million NOK (approx 200 000 USD) within 10 days. This was a Cisco installation, but misconfigured Asterisk installations are also abused a lot.