Because each request can create a billable SMS event, and attackers can generate that demand at scale with automation. The weakness is the business logic that converts a simple form submission into a paid identity action. When that trigger is weakly governed, the verification path becomes a monetisation channel.
Why This Matters for Security Teams
OTP-based verification is attractive to fraud operators because it turns user input into a paid outbound event with very little friction. When rate limits, device intelligence, and abuse detection are weak, attackers can automate submissions, trigger SMS delivery at scale, and create direct cost while also obscuring legitimate traffic patterns. This is not just a messaging problem; it is a business logic problem tied to identity verification design.
The risk sits at the intersection of fraud, availability, and identity governance. A flow that looks harmless in isolation can become a monetisation channel, a denial-of-wallet vector, or a precursor to account takeover. Current guidance suggests that abuse controls should be evaluated at the request layer, not only after the OTP is sent. NHI Mgmt Group’s research on the Ultimate Guide to Non-Human Identities shows how weak lifecycle governance and visibility gaps create compounding exposure across identity workflows, and the same pattern appears here when verification actions are not tightly governed. In practice, many security teams encounter traffic pumping only after messaging bills spike and customer support begins reporting verification failures.
How It Works in Practice
Traffic pumping fraud works by exploiting the gap between a request and the business action that follows it. The attacker does not need to defeat the OTP itself. They only need to cause the system to send it. That means the most effective controls are upstream: eligibility checks, per-destination throttles, bot detection, session risk scoring, and step-up verification before any SMS is dispatched. The standard should be to treat OTP sends as privileged transactions, not routine form submissions.
Operationally, teams should look for patterns such as repeated requests to the same phone range, bursts from the same ASN, short dwell times, or mismatches between account age and verification demand. The NIST Cybersecurity Framework 2.0 is useful here because it pushes organisations toward risk-informed detection and response, rather than assuming the verification channel is self-protecting. Where possible, integrate fraud rules with identity telemetry so that a suspicious request can be denied before the SMS vendor is called. NHI Mgmt Group’s Schneider Electric credentials breach illustrates how identity abuse becomes materially more expensive when the defensive boundary is too late in the flow.
- Apply per-number and per-device rate limits before the OTP request is submitted.
- Use risk scoring to block low-trust sessions, proxies, and automated traffic.
- Require additional proof for high-cost destinations or repeated resend attempts.
- Log OTP send volume, failure rate, geography, and carrier response codes for anomaly detection.
These controls tend to break down in high-volume consumer apps with global phone coverage because legitimate retries, carrier delays, and roaming users can look similar to fraud at first pass.
Common Variations and Edge Cases
Tighter OTP controls often increase user friction and support overhead, requiring organisations to balance fraud reduction against conversion loss. That tradeoff is especially visible in signup, password reset, and account recovery flows, where blocking too aggressively can strand real users. Best practice is evolving, but many teams now prefer layered controls over a single hard deny rule.
One common edge case is shared infrastructure. If verification is outsourced to a third-party messaging provider, the organisation may see only partial telemetry, making abuse harder to distinguish from carrier routing noise. Another is legitimate campaign traffic, where promotions or product launches can mimic attack bursts. In those environments, current guidance suggests combining OTP issuance with device binding, adaptive challenges, and destination intelligence instead of relying on raw request counts alone. The business impact is magnified when a single flow can trigger repeated sends, so resend logic should be especially conservative. NHI Mgmt Group notes that only 5.7% of organisations have full visibility into their service accounts, a reminder that hidden dependencies often make these abuse paths harder to govern than expected.
Where fraud teams and identity teams operate separately, the control gap widens because one team sees cost and the other sees authentication, but neither sees the full abuse chain.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST CSF 2.0 and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | DE.CM-1 | OTP fraud depends on detecting anomalous request patterns and cost spikes. |
| OWASP Non-Human Identity Top 10 | NHI-07 | Weak verification logic can expose identity workflows to automated abuse. |
| NIST AI RMF | Risk-based evaluation supports adaptive decisions for suspicious verification requests. |
Monitor verification traffic continuously and alert on bursts, geo anomalies, and resend abuse.
