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Comment by hwstar | Hacker News Reader

Go ahead Paypal! Just try and get past my voice/dtmf Captcha system on my Asterisk PBX with your robocaller. I whitelist friends and family so they don't have to go through the Captcha if they call. So far, I've received no friends and family robocalls, but receiving one eventually would not be surprising.

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This is awesome. I am pretty familiar with Asterisk and can think of a couple ways to do this, but I would love to see a blog post or something detailing how you accomplished this.

Seconded! Please take moment to write up how you accomplished this wizardry, for the benefit of mankind. (Or at least the Asterisk-using subset thereof...)

1. The following macro does the captcha:

[macro-captcha] exten => s,1,Answer exten => s,n(retry),Wait(2); exten => s,n,Set(pin3=${RAND(100,999)}); exten => s,n,Playback(reallivehuman); exten => s,n,Wait(1); exten => s,n,SayDigits(${pin3}); exten => s,n,Read(pinent,,4) exten => s,n,GotoIf($["${pin3}" = "${pinent}"]?ok:retry) exten => s,n(ok),Playback(queue-thankyou);

2. The whitelist jumps around the Captcha macro in the incoming context:

exten => 6199111111,n,GotoIf($["${CALLERID(num)}" = "2024561414"]?whitelist)

exten => 6199111111,n,Macro(captcha); * Do captcha exten => 6199111111,n(whitelist),Goto(inbound-calls-main,s,1);

This also buys me peace and quiet during the few days leading up to election day. (Political robocalls are what caused me to implement it).

Perfect! Your hard work has subsequently been stolen and implemented elsewhere. Thank you!

Welcome to the voice menu from Hell. We used to do that with AT&T Voice Power cards back in the day.

That only helps their stats. Robo dialing wants to avoid less than 6 second calls, and generally keep their average answer ratio and call duration up. The best bet is to answer and hangup within a few seconds

That sounds like a fun weekend project. Any good Asterisk guides or just use the official documentation? I wonder if a Raspberry Pi could handle it.

The old Raspberry Pi was able to handle 1-2 simultaneous calls with no signs of trouble. We were able to run a 3 way call between 2 lines and a cell user without problems.

The newer Pi should be capable of handling ~3-5 calls, assuming similar scaling.

I was handling 3 calls on a PIII and 256MB of ram. the Pi, especially the second edition, should handle asterisk fairly well; it actually makes an ideal PBX server!

ah yes, asterisk <3 many fond memories of running a PBX in my basement and two cisco IP phones and a crappy VOIP trunk. I remember beefing up the wakeup reminder functionality too (that might have been asterisk@home specific; before they went and became jerks)

so tempting to set that up again!

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