WASHINGTON -- Caller ID, Do Not Call registries, telephone number blocking -- all entered the arsenal of consumer weapons against telemarketers to great acclaim, only to fall from favor as growing numbers of cold-calling solicitors found ways around them.
Now, the Federal Trade Commission again says it might have found a better solution. On Tuesday, it named the winners of its first Robocall Challenge, a public contest to design a system to stop unsolicited marketing calls from reaching an individual's phone.
The winners, who split a $50,000 prize, are Aaron Foss, a software developer from Long Island, and Serdar Danis, a computer engineer who declined to reveal his hometown.
Mr. Foss conceived Nomorobo, a way to use a phone system's talents against itself to build a blacklist of threatening numbers. Mr. Danis came up with the less creatively named Robocall Filtering System and Device with Autonomous Blacklisting, Whitelisting, Graylisting and Caller ID Spoof Detection.
A separate Technology Achievement Award, with no monetary prize, went to Daniel Klein and Dean Jackson, Google engineers in Pittsburgh, for a sort of crowdsourced database of annoying telemarketers' phone numbers.
"The solutions that our winners came up with have the potential to turn the tide on illegal robocalls," Charles Harwood, acting director of the F.T.C.'s Bureau of Consumer Protection, said in a statement. "We're hoping these winning proposals find their way to the marketplace soon, and will provide relief to millions of American consumers harassed by these calls."
They might, but it will take months. Mr. Harwood said the F.T.C. was not endorsing any commercial products, and the inventors will have to deal with intellectual property issues and concerns about privacy and data security.
Mr. Foss expressed optimism about attracting an investor to help him commercialize his concept. "It still needs to be fleshed out a little bit," he said in an interview. "We'll need to see how it works with real data and real people."
Nomorobo uses the simultaneous ringing feature that is available on most phone systems and allows a user to have an incoming call ring at several numbers at once. Mr. Foss's system, he said, splits the call and routes it to a server, which analyzes the incoming data and uses "machine learning" to build a database of acceptable and prohibited numbers and calling patterns.
The system answers a rejected call, and then hangs up. Incorrectly categorized or unrecognized calls are screened before ringing through to the user.
The other winners similarly use algorithms to build a database of blacklisted numbers with which to screen incoming calls. The systems have the potential to be used on home or cellphones.
The F.T.C. and the Federal Communications Commission already enforce regulations against sending prerecorded sales calls to households without the written consent of the recipient.
Nevertheless, the F.T.C. says robocalls are its most persistent problem, generating roughly 200,000 consumer complaints each month, even though the agency says it has stopped many of the businesses responsible for the billions of robocalls made each year.
In recent years, "the technology has developed so that it's extremely cheap and easy to send out millions of calls instantly," said Kati Daffan, who oversaw the robocall project for the F.T.C.
With millions of calls and hundreds of thousands of customers complaining, do phone companies have a stake in trying to solve the problem?
"I have to wonder if it's just not a priority of theirs," Mr. Foss said. "Maybe this will shine a light on it, and the phone companies will take it seriously."
This article originally appeared in The New York Times.