Nomorobo put an end to 83 million (and counting) robocalls

Phone with checkmark


Calls analyzed per hour

User group network



Sound waveform with a close symbol


Robocalls blocked to date

There are thousands of invisible evil robots making millions of illegal calls to consumers every day. The problem has plagued consumers for decades, but the solution seemed out of grasp. That is, until October 2013, when developer and entrepreneur Aaron Foss threw his hat into the ring for the FTC anti-robocalling challenge. His solution, built on Twilio, earned him a $25,000 prize, an FTC Technology Achievement Award, and launched him on an unplanned trajectory to “fight the good fight” against robocalls with his company, Nomorobo.

Powered by Twilio, Nomorobo acts as a middleman, snuffing out illegal calls before they get to the consumer. To date, Nomorobo has blocked upwards of 83 million calls—a number that’s growing faster than we can report it. In its first 18 months, the company grew from zero to 225,000 users, and plans to hit 2 million users by 2016.

Halting a plague of nuisance calls

Consumers, the FTC, and phone carriers were all too familiar with the robocalling epidemic, but attempts to fix the problem were falling short. The “Do Not Call” list was failing to block all robocalls and carriers were pointing to regulatory roadblocks as an excuse not to block robocalls. What better way for the FTC to motivate the commercial market to come up with a solution than a developer challenge?

The rules of the FTC challenge were strict. You couldn’t change the phone system; the solution had to work on both mobile and landlines; it had to be easy to use and setup; and the number one criteria was how feasible it was to launch and get people using it as quickly as possible.

Foss delivered.

Since he’d been developing apps on Twilio since 2009, he realized it was a likely answer to solve yet another communications challenge. He built the prototype in one weekend. He perfected the solution, submitted it, and was selected as the winner out of 800 entries.

Ring, ring, click

The core to Foss’ solution is simultaneous ring. This allows multiple destinations or devices to all ring at the same time when a call is received. The first device to answer the call causes the other lines to stop ringing. For example, a person might set their office phone to simultaneously ring their cell phone so that no matter where they are, they won’t miss a call.

His “aha!” moment came when he realized that he could piggyback his solution onto this feature. Instead of using simultaneous ring with a mobile phone and an office phone, he could assign one destination as a Twilio number. Nomorobo could answer (and hang up on!) robocallers for the consumer.

After a quick, one-time setup, incoming calls are able to be analyzed by Nomorobo. If it’s a good caller, Nomorobo instructs Twilio to return a busy signal and the call continues ringing on the person’s phone, just like normal. Both the caller and the recipient don’t notice anything different from making and receiving a regular phone call.

But if it’s a robocall, Nomorobo jumps in and answers the call immediately. To prevent false positives, instead of just hanging up, the caller is presented with an audio CAPTCHA. If the caller passes the test and proves they are human, the call is allowed through. If they fail, Nomorobo hangs up the call.

Accuracy is the key to Nomorobo’s success. Detecting robocalling patterns is pretty straightforward. For example, if a certain caller has made 3,000 calls in the past 5 minutes, there’s a good chance that it’s a robocaller. But, there are plenty of legal robocalls that need to get though—weather warnings, police alerts, and school closures, for instance. Nomorobo maintains a full whitelist of allowed robocalls. These calls are never blocked.

The first ring of a call takes 6 seconds, but Nomorobo makes the distinction much faster, blocking or allowing a call within 200ms.

Since the whole service takes place in the cloud, there are no infrastructure changes or hardware required.

“Twilio makes things that were once impossible, simple.”

Aaron Foss CEO

“Before Twilio, connecting your software to a phone was nearly impossible. You’d have to dump in $5M if you were trying to build a telecom business before you even had one customer,” said Foss. “Twilio makes it so easy to integrate and manage. And, it’s incredibly affordable. We wouldn’t be in business without them.”

Currently, simultaneous ring is only available on VoIP. However, as carriers are increasingly losing landline business due to robocalls, they’re realizing the need to start supporting simultaneous ring. By the end of 2015, Nomorobo will be available on most of the major carriers.

The telemarketer terminator

Every day, Foss gets emails from fanatically happy consumers whose phones are now silent, including an 82-year old grandmother in NJ who emailed him to share how much she loves Nomorobo.

And Twilio has been battle-tested by the best bots out there. Currently, Nomorobo analyzes over 25,000 calls an hour. Twilio is handling the massive amount of traffic, and so is Foss, who continues to manage it from his desk at home.

“I’m a one-man shop, but I look at all of the 300+ employees at Twilio as part of my team. Anybody can build technology, but it’s a rare group of people that are willing to help me build my business,” he said.

Ready to get started with Twilio?