Businesses use one-time passwords to verify phone numbers, register customers, authenticate logins, and support password recovery.<\/p>\n
However, every public workflow that can trigger an SMS message may become a target when automated programs are allowed to request verification codes without sufficient controls.<\/p>\n
This type of abuse is commonly known as SMS pumping<\/strong> or artificially inflated traffic\u2014AIT<\/strong>. It can increase messaging costs, distort product analytics, consume technical resources, and affect legitimate users.<\/p>\n SMS pumping is the artificial generation of SMS traffic through forms, applications, or APIs that automatically send messages.<\/p>\n An attacker may use bots to submit large numbers of phone numbers to an OTP, registration, login, password-recovery, or app-download workflow.<\/p>\n In some scenarios, the attacker targets numbers or mobile networks from which they can benefit financially. In other cases, the objective may be to exhaust a business\u2019s messaging budget or disrupt its service.<\/p>\n Consider an application that sends an OTP immediately after a phone number is submitted.<\/p>\n An automated script may:<\/p>\n The messaging platform processes real send requests, but the traffic produces no legitimate users or transactions.<\/p>\n SMS pumping and OTP theft are different problems.<\/p>\n SMS pumping primarily aims to generate traffic and increase cost. The attacker does not necessarily need to read the code or access a customer account.<\/p>\n OTP theft aims to obtain a legitimate user\u2019s verification code through phishing, social engineering, interception, or another method, and then use it to access an account.<\/p>\n Both may target authentication workflows, but their indicators and incident-response procedures differ.<\/p>\n Registration, login, password recovery, and resend-code endpoints often send a message before the user has an established or verified account.<\/p>\n AWS describes AIT attacks as bot activity that particularly targets workflows that trigger immediate SMS sends, including login and sign-up processes. Google also identifies SMS-based two-factor authentication and phone verification as potential targets for SMS toll fraud.<\/p>\n A sudden increase in messages does not automatically prove fraud. It should be investigated alongside other signals, including:<\/p>\n Provider-side fraud systems commonly evaluate historical traffic, destination fluctuations, message volumes by number or prefix, and error patterns associated with phone-number ranges.<\/p>\n Every request that reaches the messaging provider may create a billable message, even when it does not represent a real customer.<\/p>\n Emergency restrictions introduced during an attack may block or delay real customers if they are not carefully targeted.<\/p>\n Registration and verification-request numbers may appear to grow while completion rates fall, leading to misleading product and marketing conclusions.<\/p>\n The attack consumes API capacity, database operations, logs, monitoring resources, and staff time.<\/p>\n Effective protection is layered. Application controls, destination policies, risk analysis, provider capabilities, and incident procedures should work together.<\/p>\n A limit per phone number is not sufficient because an attacker can rotate across thousands of destinations.<\/p>\n Consider separate limits for:<\/p>\n Introduce a resend cooldown and maximum hourly and daily requests. Thresholds should be based on the application\u2019s legitimate behavior rather than copied from another service.<\/p>\n Some verification platforms support programmable API-layer rate limits that block a request before channel delivery occurs.<\/p>\n Use bot-risk assessment or an appropriate challenge before the application calls the SMS API. Always validate the result on the server.<\/p>\n Cloudflare\u2019s Turnstile documentation describes a browser-generated token that must be validated by the server. Google\u2019s risk-assessment services can also provide a score that a backend uses when deciding whether to allow an SMS request.<\/p>\n Bot protection should not be the only control. It is stronger when combined with rate limits, geographic restrictions, destination analysis, and behavioral signals.<\/p>\n A Saudi-focused service does not normally need to send OTP messages to every country.<\/p>\n Use an allowlist for supported markets and introduce additional checks for unusual or high-cost destinations. AWS recommends blocking countries where a business does not operate and filtering destinations associated with higher cost or SMS pumping concerns.<\/p>\n Evaluate the full request rather than treating every user identically.<\/p>\n Higher-risk signals may include a new device, unusual location, rapidly changing phone numbers, repeated requests without successful verification, and a sudden concentration within a specific prefix.<\/p>\n Low-risk requests may proceed normally. Medium-risk requests can receive an additional challenge. High-risk requests can be blocked or manually reviewed.<\/p>\n An OTP should be:<\/p>\n A resend request should not create unlimited new messages. AWS includes a short OTP time-to-live among its SMS security best practices.<\/p>\n Track:<\/p>\n Create alerts and an emergency circuit breaker for abnormal volume or spend.<\/p>\n Where possible, use separate API credentials, reports, budgets, and controls for OTP traffic. This makes abnormal verification traffic easier to isolate without affecting order notifications and other operational messages.<\/p>\n Identify the affected endpoint, country, prefix, traffic source, and time window. Then apply targeted controls:<\/p>\n Avoid disabling all OTP traffic unless necessary. Isolating the affected destination or workflow can preserve access for legitimate users.<\/p>\n Common mistakes include limiting only by phone number, applying controls in the browser rather than on the server, allowing all countries by default, and generating a new message for every resend click.<\/p>\n Businesses should also avoid relying on CAPTCHA alone, discovering fraud only after reviewing the invoice, or using one unrestricted API credential for every messaging use case.<\/p>\n Before launching an OTP workflow, confirm that it includes:<\/p>\n OurSMS provides OTP API and SMS API services for applications and websites, together with API credentials, delivery-status reporting, and Webhooks. Businesses can use this delivery information alongside their internal verification results to build more accurate monitoring.<\/p>\n Preventing SMS pumping remains a shared responsibility across the application, the messaging provider, and the security and operations teams.<\/p>\n Before launching a high-volume OTP workflow, discuss supported countries, expected traffic, access controls, reporting, and escalation procedures with the OurSMS team.<\/p>\n SMS pumping is not simply an increase in message volume. It is the abuse of a verification workflow in a way that can consume budget, distort data, and affect legitimate customers.<\/p>\n Protection begins before the SMS API is called. Validate the request, enforce multiple limits, restrict destinations, monitor conversion, and prepare an incident-response plan.<\/p>\n The earlier suspicious traffic is identified, the fewer fraudulent messages are sent and the easier the incident becomes to contain.<\/p>\n","protected":false},"excerpt":{"rendered":" What Is SMS Pumping and How Can You Protect Your OTP Budget? Businesses use one-time passwords to verify phone numbers, register customers, authenticate logins, and support password recovery. However, every public workflow that can trigger an SMS message may become a target when automated programs are allowed to request verification codes without sufficient controls. This […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_angie_page":false,"page_builder":"","footnotes":""},"categories":[58],"tags":[],"class_list":["post-15126","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/posts\/15126","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/comments?post=15126"}],"version-history":[{"count":2,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/posts\/15126\/revisions"}],"predecessor-version":[{"id":15130,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/posts\/15126\/revisions\/15130"}],"wp:attachment":[{"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/media?parent=15126"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/categories?post=15126"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/oursms.com\/en\/wp-json\/wp\/v2\/tags?post=15126"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What Is SMS Pumping?<\/h2>\n
How Does an SMS Pumping Attack Work?<\/h2>\n
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SMS Pumping Versus OTP Theft<\/h2>\n
Why Are Registration Workflows Common Targets?<\/h2>\n
Warning Signs of SMS Pumping<\/h2>\n
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How SMS Pumping Affects a Business<\/h2>\n
Direct messaging costs<\/h3>\n
Friction for legitimate users<\/h3>\n
Distorted analytics<\/h3>\n
Operational overhead<\/h3>\n
How to Protect an OTP Workflow<\/h2>\n
Apply rate limits at multiple levels<\/h3>\n
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Protect forms from automated traffic<\/h3>\n
Restrict destination countries<\/h3>\n
Use risk-based decisions<\/h3>\n
Control the OTP lifecycle<\/h3>\n
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Monitor volume, cost, and conversion<\/h3>\n
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Separate OTP traffic<\/h3>\n
What Should You Do During an Active Attack?<\/h2>\n
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Common Mistakes<\/h2>\n
Developer Checklist<\/h2>\n
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How OurSMS<\/a> Supports OTP Integration<\/h2>\n
Conclusion<\/h2>\n