Hardware Hack Makes Robocall Blocking Service Even Better

Sorry to bear sad tidings, but your car’s extended warranty is about to expire. At least that’s what you’ll likely hear if you answer one of those robocalls that have descended like a plague upon us. We applaud any effort to control the flood of robocalls, even if it means supplementing a commercial blocking service with a DIY ring-blocker.

The commercial service that [Jim] engaged to do his landline blocking is called Nomorobo – get it? It uses the Simultaneous Ringing feature many VoIP carriers support to intercept blacklisted robocallers, but with a catch: it needs caller ID data, so it lets the first ring go through. [Jim]’s box intercepts the ringing signal coming from his Xfinity modem using a full-wave rectifier and an analog input on an Arduino. Once the ring pattern is received, the Arduino flips a relay that connects all the phones in the house to the line, letting the call ring through. If Nomorobo has blocked the call, he’ll never hear a thing. There were a few glitches to deal with, like false positives from going off- and on-hook, but those were handled in software. There’s also a delay in displaying caller ID information on his phones, but it’s a small price to pay for peace.

Any escalation in the war on robocalls is justified, and we applaud [Jim] for his service. Should you feel like joining the fray, step one is to know your enemy. This primer on robocalling will help.

Thanks to [Phil] for the tip.

69 thoughts on “Hardware Hack Makes Robocall Blocking Service Even Better

    1. From what I heard they sold it to one of the robo call centers.
      I think the goverment keep it for a year and found it was going to cost to much money.
      And thats when they sold it. Ha Ha on me and you who sined up.
      Thats one reason I keep getting the calls.
      But now I am getting people calling. NOW It Time to PARTY……
      I do my best to keep them on the phone as long as possible.
      And Boy do I have fun with them. Some times its the same guy and I get him again and again.
      So I’m doing my job right. But My wife says I have to stop, I’m making to much nose.
      I dont care. PARTY Time is is.

      And I think every one should be doing this. And have fun. Even at 2 AM.

        1. There’s a set of IVR recordings called “It’s Lenny” that are great, the system simply plays the next recording in a simple loop but that totals about three minutes, but are so we’ll done that some calls go through the loop three or more times.

          Bunch of recordings on YouTube.

      1. Yes indeedy! Tie up their time to cut down on the amount of people they are trying to scam. They say it’s better to just hang up or not answer at all. However, once your voicemail picks it up, it is more than likely showing them that it’s a live phone line anyway! I have Nomorobo and it doesn’t pick up and disconnect the local spoofed numbers which is the bulk of what I receive. Hope the Traced Act works, but it won’t be long before they find a way around that too. My companion thinks I’m nuts, but if they are going to waste my time, I’m surely going to waste theirs! And a scammer is not ever going to check a no call list, as they are sooooo above the law you know. So give them HELL and keep that party going!!!

  1. We completely deprecated our landline. We still have it, mainly because I’ve had the number for almost 30 years now, but the ringer is shut off and voicemails are just emailed to us.

    1. I’d like to get rid of my landline, but my companion doesn’t have an active cellphone right now and I have to keep it. Damnit! Nothing I hate more than having to pay to get harrassed!

    2. Port your # to google voice, free, selective forwarding of calls to other phones, voicemail with transcripts, text and email notifications of calls. I’ve had one since it came out, it filters out a lot of spam calls and then forwards the call to my cell and my Ooma home phone line. An Obihai device (around 30-40) can make a landline phone into a google voice phone. When I change cell phones, I don’t have to port the old cell #, just add the new cell number to the google voice forwarding list and delete the old one.

  2. My voip provider have rule based filtering/blocking/white listing via their website UI. There is no need for silly hacks on my side. I haven’t these calls for a few years now.

    I can do wild card filtering/blocking e.g. block country/area code or the individual number, block on invalid/no callerID. The filtered number can be redirected to voice mail/”busy signal”/”number not in use”. I added the usual election calls and if anything else came through to the rules.

  3. I have an accidental and nearly foolproof method of avoiding robocalls. Most of them use the same area code as your own phone and spoof it so it looks like one of your neighbors might be calling. But in my case, my phone has a completely different area code, so if it isn’t my brother, I can ignore the call without a second thought. And since I don’t pickup for any other calls I don’t recognize, I’m good.

    Sometimes I do answer them anyway though, just so I can screw with the scammers. I like to see just how long I can keep them on the line before they finally hang-up in frustration. IMO, I think if everybody did that it would change their financial model enough to make it more costly for them to engage in robocalling.

    1. I managed to keep some Indian idiots that worked for “microsoft” who detected malware running on my computer for an hour and 15 minutes before he transferred me to their second level team. That new guy got mad at me for wasting his time after another 15 minutes and hung up on me.

      I call them back every once in a while when they leave a vm with a number to call back.

      1. I love to pretend I am one of those TV evangelists, er phone evangelist. I have a whole spiel I give them. I have never had a phone call go more than 3 minutes before they hang up. They usually hang up after the line where I tell them to hit themselves in the forehead with the receiver so that I may heal them.

        1. That’s hilarious! If enough people would do stuff like this, it may provide enough chaos to make it not worth their while to pester us like they do. That won’t happen, but you’re tying up their time so there’s a few more people that they won’t have time to scam that day! I’m self employed and I get the Google business listing scam call every week. I’m a dog groomer and have a blower dryer that makes a hell of a noise when you blow it into the phone. When they say, “I’d be happy to help you with your Google business listing”, I let them have it! Don’t know how many eardrums I took out, but they called right back the next week. Absolutely relentless.

      2. LOL, I too got a call from Bob at the Windows Corporation, to say I had malware but he would fix it for me. I told him I was a VP from the Windows Corporation and wanted his name and badge number so I could recognize him for this amazing proactive service I’d never heard anything about. I think he retroactively hung up.

    2. These are schmucks who can’t get any other job. Sometimes I ask them if their mother knows their son is a criminal. But if it’s “windows”, I’ll spend ten – 20 minutes “booting up” (“it’s slow, because of the ‘viruses’, I guess”), then I’ll go to the toilet with the phone & give them an earful (extra points for a #2!) . Then I’ll play along right up until they want the password to Teamview into my machine, then I admit I run Linux. I’ve learned some new Hindi words that way.

  4. It is a criminal offense to connect non-certified devices to the PTSN network. Voip is likely a grey area, such as a PBX interface or a VOIP ATA adapter from your local cable provider but to hook something like this to a traditional landline is definitely illegal. Enhanced Communications Services has already looked at this “solution” about 3 years ago but it’s still has a fatal flaw in it’s design– Caller ID can still be spoofed and as long as it can, this can never be a good solution, but it does seem better than nothing. I provide a simpler solution which is not for everyone, but works for people like myself. Change your area code to something you never get calls from, then block all calls from that area code unless it’s in your contacts. This stops 100% of neighborhood spoofing calls which most people seem to be getting these days. Remember, any solution that uses caller ID lockups is fatally flawed. I’m working on the ultimate solution that can verify if caller ID is indeed accurate. Once you have accurate and verified caller ID, then and only then can you trust call discrimination but it still doesn’t verify who is behind the lines. Remember also, that the SHAKEN/STIR implementations only apply to US carriers and will not work on landlines that I know of. Our government needs to have smarter people at the helm than the ones they have deciding which technologies or methods are employed to protect consumers against fraud. No law against telemarketers and other unwanted calls will ever stop the abuse on a network of networks that never was designed to handle call verification and call authentication schemes. And what happens when the internet isn’t available when a call is to come through? What if Nomorobo or another 3rd party Caller ID lookup service were to inadvertently tag someone’s number as a robocaller? I could spoof thousands of calls from an adversary and trigger these companies to classify any number I want as a “likely spam” or something along those lines. What happens if 911 dispatch were to return a call that was made to them, and got disconnected? They would never know the call wasn’t actually ringing through. I have so many questions and concerns about a DIY solution like this because my team has already been working to address the problem.

    1. I used cat 6 cable instead of certified phone wire to wire up my telephone, and I used my own double-sided tape to attach the RJ11 connector to the wall instead of the provided tape. I don’t believe that I stripped the exactly correct amount of insulation from the wires, so clearly I have a major violation there. The warranty has expired on my phone and there is no maintenance contract, so really there is no way for me to tell if my phone is legal or not, I can only guess. The foam bits have worn away on the headset so clearly there is some sort of compliance issue. Perhaps the worst sin of all, the power supply on my phone blew out and I replaced it with a different one.

      Please come and arrest me now.

    2. There’s a big difference between voltage (POTS phone line) and data (VOIP). You could damage Ma Bell’s hardware if you did something screwy with an old-fashioned landline (which is actually hardwired into their switching system), but you’re not able to do any damage if you’re sending goofy data down your VOIP internet connection through a cable modem. A POTS line is about 5 volts when off-hook, about 90 volts when ringing. And POTS would limit you to 5 phone ringers to limit current draw (modern “ringer equivalencies” are usually rated on the phone, and are a tiny fraction of what used to be 1 ringer). Today you could have 50 VOIP phones ringing and no one would care. VOIP is data. Worst you could do with a VOIP phone is blow up your own stuff (unless you start shooting voltage down your cable connection).

    3. He’s not hooking anything to the PSTN. You misunderstood. Disconnect the wire outside from the PSTN. Then use Your internal phone wiring for regular phones connected to a VOIP adapter like OBI which connected to your internet and can use free Google voice ( your number can be ported to GV for free.

  5. There’s an app called RoboKiller that automatically forwards the call to a fake pickup that runs hilarious AI audios to keep the scammers on the line. For a good laugh, check their samples out on YouTube.

    1. If you work from home, you should have a land line. It’s bad enough that you have to attend meetings on the phone, noisy connections and dropped calls will not make your co-workers happy. Do you really want to have the connection drop in the middle of your performance review?

        1. I used vonage for about four years. Their $9.99/month was never $9.99/month. “Oh those are regulatory taxes that we have no control over.” So from the get-go I was paying more like $13/month. My wife pays the bills so I didn’t notice that a couple times a year they’d bump up the price by a dollar or two.

          I had a look at our bill one month and was shocked I was paying about $30/month. I called them up to cancel and they said: hey, we value you as a long time customer. How about I change your bill to $9.99/month? That is like catching your girlfriend cheating and she says: I love you so much I will stop sleeping with other men now. Too damn late.

          I’m now a happy ooma customer. Vonage will never see a penny more from me.

          Oh, and I periodically had problems with vonage call quality. Never with ooma.

      1. >Do you really want to have the connection drop in the middle of your performance review?

        Uh, unless you work for the world’s most anti-technology company, I’m pretty sure you would only use phone of any kind as a last resort.

        Zoom, or Google Hangouts, are pretty much the norm.

  6. I have a landline I rely on for work in scotland, the landline was getting hammered with nuisance calls, id say 9/10 of them were from london or no i.d. so I just blocked all calls from london and all calls with no i.d. Not ideal but worked for me, seems this is a world wide problem.

      1. And the beavers in Canada as well. There fortifying there dams.

        I’m having to much fun today.. Just got a call from the bank saying I’ve been hacked and could I verify my Information. Party time.

        OH, Oh Oh. …. I use disposable credit cards when I order online. They are a blast. ” But sur there is only .12 on the card.”

        1. Scammer trolling gets old. But I lately got a nice young lady, thick Indian accent, wanting to fix my iTunes account or something. Said she was an Apple expert, so I asked her what semi-dwarf variety I should plant in a clay soil with a pH of 7 in Zone 5 ….. silence ….. click…

  7. The VOIP service I use allows me an unlimited number of blocked numbers. The problem is that these douchebags are now spoofing the caller ID data using local numbers, including ones I know and even my own number at times! I simply can’t block them all, so I’ve stopped trying. Instead I now answer calls from numbers I don’t recognize with a stern, “May I help you?”, which seems to cause some of their computers to hang up on me, as they were probably looking for a”hello” instead.

    I guess what I don’t understand is why it is legal (or is it?) for these jerks to spoof caller ID. Isn’t that the same as using a fake ID anywhere else? If not, why isn’t it?

    1. It’s illegal to spoof a number for fraudulent purposes. Sadly the technology has fallen into the wrong hands. Should we ever think that it wouldn’t? They are real good at getting a hold of whatever they want and not get caught.

    2. I have a box I bought on amazon that does whitelisting and blacklisting. I put it on the line, active but blocking disabled. After a few weeks, everyone that I know has called, I add all of those known numbers to the whitelist and turn the blocking on. Anyone that calls on the whitelist gets ringed through. Otherwise they get “We don’t take calls from telemarketers here, so remove us from your list, or press 1 to ring through if you know the recipient”. I had all of ONE guy think he could press 1 and I let my dog bark at him until he hung up. Most of them are autodialers, so they just hang up as they think its an answering machine. After a year or two, I seem to have been removed from most lists as “non responsive”.

  8. There is a MUCH easier hack for achieving the same result – just get a phone that allows custom ringtones, and make a ringtone that begins with 5-7 seconds of silence.

    Years ago, we ported our landline to a (free) Google Voice account, and bought a $50 Obihai box that is essentially an ATA. So phone bill is exactly zero, and the service is great. Art a $6/year charge for 911 service and about $10/year for the Jolly Roger anti-spam AI bit service, and it is the best way to have non cell service. Our phone only rings when it is a whitelisted number, others are prompted to either leave a message, or forwarded to spam bots, depending upon their score in a CNAM-based weighted system.

    The JR bots are so darn funny, too – I started posting the number on MLM and general public forums, just to try to drum up more victims. The more time they waste talking to bots, the less time they have to call everyone else, and the more chuckles I get listening to a scammer try to sell an extended warranty to IBM Watson.

    1. “The more time they waste talking to bots, the less time they have to call everyone else, and the more chuckles I get listening to a scammer try to sell an extended warranty to IBM Watson.”

      And people wonder why Skynet hates us so much. BTW I have that box. Good service.

      1. “Listen, and understand. That terminator is out there, it cant be bargained with, it cant be reasoned with, it doesn’t feel pity or remorse or fear, and it absolutely will not stop… EVER. Because some a-hole kept forwarding it robocalls.” —Kyle Reese

  9. Somehow I don’t think those relays are ACMA approved.

    If you do go ahead and install this, be _very_ careful who you tell about it, because fines could be issued for non-compliant devices and wiring.

    1. Just like the fines they levy on scammers? Which they are WAY behind in prosecuting and collecting. Yet our politicians have raised the fines (that they don’t collect), patted themselves on the back and reminded us to vote for them again.

      1. Well, the scammers defend themselves with a “You’re gonna prosecute us? Like all the hobbyists out there with non-compliant equipment connected?” And the charges disappear in a puff of logic.

  10. There is another method: When a call comes in generate a random number, answer the call and request that the caller enter the number on their keypad.
    i.e. upon calling an automated system says something along the lines of: To contact this number please enter the following combination one-two-zero-two. Upon entering the correct combination the call is transferred to the real telephone.

    1. That’s kinda the way NoMoRobo works, but it’s a fixed number. If you had a machine to do that on your own premises, you could program it to change the number. And give your own message.

      Hmmm, the hard part might be the interface for your phones. Generating a ring, duplexing, passing the CID, etc.

  11. I have been using voip.ms for over 5 years now, with an ivr configured to block all the spam calls. When they call they get a message saying “Press 1 to continue” in my voice. And the spammer auto dealers miss out on the press 1, I never hear from them. If you press 1, then the house phones will ring. For people we know, I have it setup to bypass the ivr. This has stopped all spam calls.

    I got the idea for this from here years ago


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