Have you ever answered your phone only to hear an ominous message about the “IRS” demanding money, warnings from “Microsoft” that your computer needs immediate repairs or from “Rachel from card member services” offering a lower interest rate on an unnamed “credit card account”?

Of course you have. And probably more often than you realize. According to telecommunications services provider YouMail, Americans received almost 2.5 billion robocalls last year, generating as much as $350 million in consumer fraud.

It’s little surprise that robocalls are the No. 1 consumer complaint filed with both the Federal Communications Commission and the Federal Trade Commission. And both Ajit Pai and Maureen Ohlhausen, the newly appointed chairs, respectively, of the two agencies, have long pushed for aggressive actions to better protect consumers from robocallers, or what Pai referred to Tuesday as “that scourge.”

But ending the epidemic will require both legal and technical solutions. Many robocalls are merely unsolicited appeals from survey firms, charities or other forms of direct marketing. But the vast majority, perhaps as many as 99 percent, are scams, whose perpetrators impersonate or “spoof” what appears to be a local telephone number to fool caller-ID systems.

That’s according to Aaron Foss, founder of a popular anti-robocall service called Nomorobo, which maintains a constantly updated blacklist of fake phone numbers and blocks unwanted and illegal calls directed at the company’s users.

I’ve been using Nomorobo on my home phone for about a year. I used to get at least a few and sometimes as many as a dozen robocalls every day, often from the same fake numbers. Now I get almost none. And as far as I know, the system has never hung up on anyone I actually wanted to talk to.

Foss’s story is a classic tale of innovation in the start-up economy. A self-described serial entrepreneur, Foss was at loose ends in 2012 when he heard by chance about a contest sponsored by the FTC to find technical solutions to the robocalling epidemic.

The agency, which in 2003 launched its Do Not Call Registry, was understandably frustrated to find the list was only being honored by legitimate marketing services while fraudsters openly flouted it. And beyond the sheer volume of violations, many if not most abuses of Do Not Call come from outside the United States, effectively beyond the agency’s reach. Consumers were swamping the agency, which found itself challenged by rapidly changing technology shifting traditional analog voice communications to digital and mobile networks.

Foss had no prior experience with telecommunications, but decided to give the contest a try.  His solution, developed over a weekend, was a clever hack based on a feature offered by new digital voice networks known as simultaneous ringing, which allows consumers to have incoming calls routed to multiple phones.

By specifying Nomorobo as one of those numbers, Foss’s service can check the caller ID against its database and disconnect calls originating from numbers on the blacklist. (If the caller is in fact a human, they have the option to identify themselves and the call goes through, putting the number on a whitelist.)

Nomorobo was one of two winners of the FTC contest, for which Foss received $25,000 to start building his business. Four years later, the company now has 850,000 users and a small staff, and has raised about $2.5 million in venture funding. The home phone service is free, with a small monthly charge for a new mobile version that today runs on Apple phones and soon on Android.

Over the past 18 months, according to data the company shared, Nomorobo has answered nearly a half-billion calls and blocked about 40 percent of them, with an accuracy rate of 95 percent. Some VoIP providers, including Ooma, Sonic and Bright House (now part of Charter), are licensing the database and blocking robocalls before they even ring on the customers’ phone, much as email spam filters do.

Still, there are limits to the service, which Foss himself described as more of a “proof of concept.”  Nomorobo can only work with digital networks that offer simultaneous ringing, or on mobile operating systems that allow users to specify a calling blacklist, a feature Apple didn’t support until the release of iOS 10.

As email users know, moreover, maintaining accurate blacklists and whitelists is time-consuming.  Errors are hard to undo. The criminal enterprises that are exploiting voice networks, meanwhile, are skilled at adapting to new technologies, locked in an escalating arms race with providers.

That’s why the FCC last year formed a Strike Force of carriers, manufacturers and equipment makers, tasking them with developing longer-term solutions to the robocalling problem that will work across networks.

The group has been working since the summer with leading Internet standards groups to secure caller ID systems to stop spoofing, develop technologies that would block unwanted and illegal calls at the point of origin, educate consumers on existing tools and provide guidance for regulators trying to accelerate deployment of new technologies.

Richard Shockey, who chairs the group developing secured caller ID, said implementation across digital networks will require at least a year, including extensive testing. “It’s not exactly changing the tires on an aircraft mid-flight,” Shockey said, “But you do want to be careful since this is actually the voice communications network of the United States.”

Some of the Strike Force’s findings may also require changes to FCC rules or possibly federal laws such as the Truth in Caller ID Act and the Telephone Consumer Protection Act. Regulators will also need to step up prosecution of illegal behavior, including financial scams as well as violations of Do Not Call.

In the meantime, lists compiled by both wired and wireless trade groups can help consumers navigate a growing array of services, many of them free, that reduce the robocall problem to something more manageable.

The crusade against robocalling is a rare creature in Washington, a win-win effort inspiring praise from both Democrats and Republicans, as well as consumer groups, legitimate marketing organizations and from every corner of the Internet ecosystem. The only group unhappy with the progress, no doubt, are those using technology to break the law. But for once, they’re not saying anything.

As for Nomorobo and its impressive “proof of concept,” Foss is sanguine about the future. “Criminal organizations will always find ways around anything. So the need for innovative technologies will never go away,” he said. “But if I do my job right, I put myself out of business.”

For the sake of frazzled consumers, let’s hope he’s right.

Read more from The Washington Post’s Innovations section.