T-Mobile and Sprint are delivering number verification to better protect customers against scams and unwanted robocalls with new cross-network protection built on STIR/SHAKEN standards.

The acronym stands for Secure Telephone Identity Revisited (STIR) and Signature-based Handling of Asserted Information Using toKENs (SHAKEN).

The new anti-robocalling feature is currently rolling out to T-Mobile and Sprint customers and will ensure that calls from the Sprint network to the T-Mobile network (and vice versa) are really coming from the number listed on their caller ID display and are not being spoofed.

T-Mobile was first to announce readiness for the FCC-recommended STIR/SHAKEN standards in November 2018 and first in the wireless industry to implement STIR/SHAKEN when it launched Caller Verified on the Samsung Galaxy Note 9 in January 2019. T-Mobile's STIR/SHAKEN implementation works across four networks: Comcast Xfinity Voice home phone service, AT&T Wireless, Inteliquent and Sprint.

T-Mobile also announced that Caller Verified is now operable across 23 smartphones, with more coming soon. The company's customers with these devices and the latest software update will automatically see “Caller Verified” on their screens for non-spoofed calls from the T-Mobile and Sprint networks.

Sprint also offers customers Sprint Call Screener Basic, a free service that identifies unwanted malicious calls and permits users to block them, and the more feature-rich Sprint Call Screener Plus premium service. In addition to the services provided by the free service, Sprint Call Screen Plus also displays a texter’s name or a caller’s name, city and state, even those not listed in contacts; identifies, blocks, and reports calls that are lower-risk, but still a nuisance; categorizes incoming calls as spam, robocalls or fraud calls; reports an individual phone number as spam; and keeps history of blocked and risky numbers.