Technically. For a network there is gear that can do it. Radware among one of 
them and the one we use via our carrier and it works. An effective defense has 
to have a larger pipe somewhere with mitigation services at a capacity well 
above your capacity.

I don’t think the CAPTCHA would work, the person just calls and calls tying up 
the available trunks. You’d need the CAPTCHA to be on the attacker’s end. Based 
on the description I got they aren’t caring about an answer they are 
essentially just trying to keep the lines always busy.

Matthew Loraditch
Sr. Network Engineer
p: 443.541.1518
w: | e:
From: Anthony Holloway <>
Sent: Monday, April 16, 2018 11:23 AM
To: Matthew Loraditch <>
Subject: Re: [cisco-voip] Robo Call DoS

Technically or legally?

How does one stop a DoS attack on a network?  Or on anything for that matter?  
Say you were attending a protest, and someone is blowing an air horn in your 
ear<>?  What can you do?

Technically, you could front end the whole thing with a captcha style gate, so 
you could ask to push a single button, button combination, or solve a simple 
addition problem resulting in two digits.  granted, just like on the web, a 
captcha is burdensome to the user, but generally, it's preferable over the site 
being down, or disrupted.

CUC and UCCX both could handle this task, though it would be easier in UCCX.

On Mon, Apr 16, 2018 at 9:49 AM Matthew Loraditch 
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

p: 443.541.1518<tel:443.541.1518>








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