Detecting scammers using the "ploop" sound

General Help
1

I have noticed that near to 100% of my inbound scam callers when you pick up the line and announce (“Good afternoon, XYZ company. This is Joe”) that there is silence, a “ploop” sound (don’t know what word to use to describe it) and then the scammer is connected.

A quick google implies that the sound is the asterisk teleconference connection sound, telling you that you have been dropped into a conference room. I don’t use teleconferencing so I have no experience there. If my research is incorrect, perhaps someone could help there.

It occurs to me that if you could detect that sound, that it would be trivial to build a filter that would block all that use that method. (Or redirect them to Lenny!)

Does anybody know if there is a “detector” for that specific sound?

2

Pragmatically, I have found that if I get a call from a previously unknown number, I don’t say a thing, real people will soon say “hello?” or some such, then I further process with STT, bots mostly move on as they are looking for a ‘mark’ who speaks or start talking for more than a few seconds, this is ‘spiel’ but not human, if the call is still ‘up’ and the sSTT is cogent, then send to your ivr/queue/whatever

3

On lines where I use an IVR I don’t have any issues. The IVR blocks all auto-dialed calls. At least so far!

This occurs on one line that I currently have ringing directly through. I’m debating just adding an IVR to it as well for previously unknown numbers.

Ideally I want to reduce friction for regular callers but I guess that is not the reality of the world today.

4

Build and maintain a whitelist of regular callers in the asterisk sqlite3 database, they will only be inconvenienced once.

5

I have a “greylist” feature that I wrote and am testing on one line. I wrote my own because I could not find one out there that I liked.

The first time a particular CID calls it is sent to a “Try again later” message, but I could send it to an IVR if I wanted. The second time it is allowed to ring through. Numbers will expire off the greylist after a period of time.

Once I’m happy with the behavior of the greylist feature I’ll deploy it to some other lines.

6

IWFM, Another strategy I used before going STT, is to ask the caller to DTMF the number (CID) they are calling from and if a ‘fail’ send to ‘secondary examination.’ . Actually just asking for the area code is pretty damn effective with less ‘friction’

7

Thank you! I have been trying to figure out what that sound is! Every time I hear it, I know it is a scam call… but I always wondered why that sound was there. I’ve never been able to google the correct term to find it.