[cisco-voip] Robo Call DoS

[Balk, David]

I have had this happen a few times in the past.

Scenario:

·        Pay day loan scam, the caller knew the users name and work number, demanded to talk to them to get them to pay.  When refused, they sent 4 or 5 simultaneous calls to the users work number (usually main department numbers) tying up that department.

Created a UCCX script that compared the callers ANI to a list of known ANIs that they were using, if it matched, it would answer and play a 30 second busy signal wav file.  The reason for answering was to tie up all of their calls and not actually ending them.  In our experience they never used more than a handful at the same time.

If the call did not match the list of known ANIs, then the call went to a menu where the caller would have to enter a digit to be connected.  This stopped the robo calls from getting through to the actual user or department. I built it with text to speech for the digit incase I needed to switch the digit on the fly without having the user re-record the greeting.  It never came to that level of need.

The menu does not stop the actual caller from pressing the digit and trying to get their money, but it does stop the robo calls.

This was back in the MGCP/PRI days.

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Matthew Loraditch
Sent: Monday, April 16, 2018 9:45 AM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] Robo Call DoS

So this is a curiosity question, we had a prospective client call us who is essentially getting robocalled to oblivion. Some scammer has robo dialers setup and is flooding all of their trunks. He got a ransom, stopped and then started again. He was originally using one number and then when the telco blocked that switching to random sources.
Are there are any legitimate defenses to this sort of thing?


Matthew Loraditch​

Sr. Network Engineer


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