Transaction Network Services (TNS) today released its 2026 Half-Year Robocall Investigation Report, which finds that while STIR/SHAKEN has driven meaningful progress among leading Communications Service Providers (CSPs), authentication alone is insufficient to stop today’s continuously evolving fraud threats.

As AI fuels increasingly sophisticated and scalable robocall attacks, fraudsters continue to exploit weaknesses throughout the ecosystem, undermining trust and enabling even highly authenticated calls to be spoofed, impersonated or unwanted.

Drawing on data from more than 1.9 billion daily call events across 150-plus CSPs and nearly 300 million subscribers, TNS finds the voice landscape to be mature in some areas, vulnerable in others, and altogether under growing pressure from bad actors leveraging artificial intelligence.

Authentication Is Working — But It’s Not the Whole Answer

Nearly three years after full STIR/SHAKEN enforcement for both large and small CSPs under the TRACED Act, results are uneven. The top seven U.S. CSPs have stabilized at approximately 85% signed inter-carrier traffic – up just 1% since mid-2025 – with the majority at the highest “A” attestation. Non-top-tier CSPs, however, are hovering at around 20%, which is a figure that reflects the real cost and infrastructure barriers many smaller CSPs face as they work toward full IP migration.

The gaps have real consequences. Invalid numbers, including unallocated, Do-Not-Originate and not-in-use lines, still receive “A” attestation in roughly 1.6% of cases. Between 10–12% of all Verstat-passed traffic is tagged as unwanted. Most strikingly, 17% of confirmed spoofed calls carry “A” attestation labeling, which means the industry’s primary trust signal is being actively exploited.

The conclusion is clear: attestation is not a guarantee of legitimacy. For enterprises and contact centers that rely on branded calling and high answer rates, layered voice security – not just compliance – is essential.

Fraud Is Evolving Faster Than Compliance

Even as CSPs shore up compliance, bad actors are raising the stakes. AI-generated voice cloning, multimodal attacks and SIM box fraud operations are making scams more convincing, targeted and scalable than ever, with automated tools turning what once required human effort into full wide-scale fraud.

Scams tracked in the first half of 2026 illustrate the breadth of the problem: fake World Cup ticket offers, utility shutoff threats targeting seniors, voice-cloned family impersonations, and AI-scripted IRS calls promising phantom refunds in exchange for banking credentials.

These campaigns orchestrated by bad actors don’t just steal money. They erode trust in every legitimate call a business, government agency or other institution such as a utility company or bank makes, threatening the long-term viability of voice as a channel.

A Key Takeaway: Collaboration Must Continue as Tech and Fraud Tactics Evolve

“The voice communications ecosystem is at a critical inflection point, and the window to act is now,” said Seth Walton, General Manager, TNS Communications Market. “STIR/SHAKEN laid a vital foundation, but building true resilience requires layered defenses, from reputation scoring to anomaly detection, spoof protection and deepfake detection. Closing the remaining gaps is a shared challenge, and we see our role as a partner to service providers and enterprises at every stage of that journey. By embracing continuous improvement across the entire ecosystem, we can build an environment where trust endures no matter how the threat landscape evolves.”

STIR/SHAKEN has moved the needle for larger CSPs, but it was designed as a foundation, not a complete solution. Now, as smaller CSPs are still working to catch up, the seams are showing. For instance, legacy TDM/SS7 switching infrastructure strips call signatures mid-route, breaking the chain of trust. At the same time, smaller CSPs navigating genuine cost and operational constraints have delayed IP migration, creating gaps that bad actors are now actively exploiting. Even where the framework functions as intended, over-attestation and abuse are eroding confidence in the very signals it produces.

Regulators are responding by tightening Know-Your-Upstream-Provider (KYUP) obligations, targeting non-IP network gaps and removing errant CSPs from the Robocall Mitigation Database. Enforcement alone, however, cannot keep pace with the growing levels of fraud, including AI-enabled fraud, which are escalating the issue. Closing these gaps requires the entire ecosystem to go further by combining compliance with analytics, reputation intelligence and adaptive defenses that evolve alongside the threat.

The TNS 2026 Half-Year Robocall Investigation Report is now available for download.

About TNS:

TNS is a global leader in trusted communications, helping operators, enterprises and consumers exchange information with confidence. Backed by deep industry expertise and global reach, TNS is enhancing trust in communications while helping customers modernize and grow in an increasingly connected world. The company’s cloud-based platforms combine advanced call analytics, digital identity and numbering intelligence to help wireless and wireline operators detect and mitigate robocalls, strengthen fraud prevention, and enable secure, branded customer engagement. Trusted by operators, enterprises and organizations around the world, TNS analyzes 1.5 billion daily call events to help keep networks, devices and applications connected and protected. For additional information visit: https://tnsi.com/resource-center/communications/.

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