Hoping to fight a growing plague of robocalls, a dozen phone companies including the country’s biggest mobile and broadband providers agreed on Thursday to adopt new call-blocking technology and other measures to help regulators track down swindlers.

As part of a pact with 51 attorneys general from across the country, the companies said they would install technology intended to stamp out the calls before they reached consumers, who have long railed about the flood of robocalls that reached 4.7 billion in July, according to YouMail, a call-blocking service.

“Robocalls are a scourge — at best, annoying, at worst, scamming people out of their hard-earned money,” said Josh Stein, North Carolina’s attorney general, a co-leader of the coalition with the attorneys general from New Hampshire and Indiana. “By signing on to these principles, industry leaders are taking new steps to keep your phone from ringing with an unwanted call.”

The new agreement — which covers Verizon, AT&T, T-Mobile, Sprint, Comcast and other providers — builds on work many are already doing to roll out technical standards that would help ensure that callers are using legitimate phone numbers. Currently, scammers often display bogus numbers — sometimes spoofing local or official numbers, like the Social Security Administration — to tempt targets into picking up the call.