Two major U.S. carriers, AT&T and T-Mobile, announced this morning a plan to team up to protect their respective customer bases from the scourge of scam robocalls. The two companies will today begin to roll out new cross-network call authentication technology based on the STIR/SHAKEN standards — a sort of universal caller ID system designed to stop illegal caller ID spoofing.

Robocalls have become a national epidemic. In 2018, U.S. mobile users received nearly 48 million robocalls — or more than 150 calls per adult, the carriers noted.

A huge part of the problem is that these calls now often come in with a spoofed phone number, making it hard for consumers to screen out unwanted calls on their own. That’s led to a rise in robocall blocking and screening apps. Even technology companies have gotten involved, with Google introducing a new AI call screener in Android and Apple rolling out Siri-powered spam call detection with iOS 13.

To help fight the call spoofing problem, the industry put together a set of standards called STIR/SHAKEN (Secure Telephony Identity Revisited / Secure Handling of Asserted information using toKENs), which effectively signs calls as “legitimate” as they travel through the interconnected phone networks.

However, the industry has been slow to roll out the system, which prompted the FCC to finally step in.

In November 2018, FCC Chairman Ajit Pai wrote to U.S. mobile operators, asking them to outline their plans around the implementation of the STIR/SHAKEN standards. The regulator also said that it would step in to mandate the implementation if the carriers didn’t meet an end-of-2019 deadline to get their call authentication systems in place.

Today’s news from AT&T and T-Mobile explains how the two will work together to authenticate calls across their networks. By implementing STIR/SHAKEN, calls will have their Caller ID signed as legitimate by the originating carrier, then validated by other carriers before they reach the consumer. Spoofed calls would fail this authentication process, and not be marked as “verified.”

As more carriers participate in this sort of authentication, more calls can be authenticated.

However, this system alone won’t actually block the spam calls — it just gives the recipient more information. In addition, devices will have to support the technology, as well, in order to display the new “verification” information.

T-Mobile earlier this year was first to launch a caller verification system on the Samsung Galaxy Note9, and today it still only works with select Android handsets from Samsung and LG. AT&T meanwhile, announced in March it was working with Comcast to exchange authenticated calls between two separate networks — a milestone in terms of cooperation between two carriers. T-Mobile and Comcast announced their own agreement in April.

The news also follows a statement by Chairman Pai that says the FCC will sign off to approve a T-Mobile/Sprint merger, as has been expected.