International Revenue Share Fraud (IRSF) is a form of telecom fraud in which criminals deliberately generate high volumes of calls or messages to international numbers that return revenue to the terminating party. Fraudsters exploit international interconnect agreements and high traffic landing charges to make money, while operators, carriers and enterprises incur the losses.

IRSF is typically conducted by organised and increasingly sophisticated criminal groups. It is often the financial end-point of several attack methods, including PBX hacking, SIM-server abuse, subscription fraud, SIP-trunk compromise, and artificially inflated traffic (AIT). Even small bursts of test traffic can quickly escalate into major financial exposure if left undetected.

Symmetry Shield is continuously enriched with high-risk voice and SMS numbers and ranges identified as being used, promoted or tested for fraudulent activity. Our intelligence combines human and automated techniques to carefully and continuously curate fraud intelligence.

This dual approach allows Shield to maintain one of the most accurate and up-to-date IRSF intelligence datasets available – enabling operators, carriers, CPaaS providers and enterprises to stop attacks before they escalate.

RSF is the financial engine behind many telecom fraud schemes. Criminals use a variety of access methods to force voice or SMS traffic toward high-tariff destinations, or even low-tariff routes where sheer volume generates the desired income. While these schemes may appear different on the surface, the underlying driver is the same: revenue-share monetisation.

By detecting and blocking high-risk numbering ranges at scale, Shield helps prevent not only IRSF itself but also the broader fraud types used to trigger it, including:

• Subscription fraud and SIM-server abuse
• PBX and SIP-trunk hacking
• Artificial Inflation of Traffic (AIT) / SMS pumping
• OTT, CPaaS and API-driven attacks that terminate into PSTN IRSF destinations
• One-time password (OTP) fraud and bot-driven test calls/SMS.

Stopping IRSF at its source disrupts the entire fraud chain, reducing financial exposure, improving service quality, and protecting both operators and enterprise customers.

Telecom operators and enterprises can use Shield’s continuously updated database of high-risk numbers to detect IRSF and other international calling fraud at every stage of the event – in routing, during live traffic, or through post-event analysis. When a call or SMS matches one of Shield’s specified numbers or high-risk ranges, it becomes immediately identifiable as suspicious, allowing operators to take automated or manual action.

Beyond real-time detection, Shield also supports proactive prevention. Its intelligence helps teams analyse traffic patterns, understand emerging fraud campaigns, and investigate related numbering behaviour. This enables operators to stop attacks before they escalate, and ultimately deter fraudsters by reducing the likelihood of successful monetisation.

Yes. Shield provides access to one of the world’s largest and continuously curated databases of high-risk IRSF voice and SMS numbers and ranges. By integrating this intelligence into your routing, fraud management or telecoms service management systems, you can automatically or manually block suspicious numbers and ranges before traffic completes.

This prevents successful fraud attempts, reduces financial exposure, and deters criminals from repeatedly targeting your network or enterprise services.

Historically, fraudsters promoted blocks of high-tariff international numbers under the label International Premium Rate Numbers (IPRN). The term was misleading: these numbers were not true Premium Rate Services (PRS), which are tightly regulated and associated with legitimate content or service charges.

Fraudsters appropriated the “premium rate” terminology to signal that certain destinations offered lucrative revenue-share payouts, even though the numbers themselves were simply normal fixed or mobile ranges in high-cost countries.

As PRS regulations strengthened and fraud controls improved, many of the actors involved in early PRS frauds and grey route operators, shifted toward what is now known as International Revenue Share Fraud (IRSF). The industry moved away from the “IPRN” term to avoid confusion with legitimate PRS services and to better reflect how modern fraud actually works.

Today, fraudsters increasingly target low- and mid-tariff destinations where they can drive large-scale volume or exploit weaker operational controls. Because termination rates no longer reliably indicate risk, rate-based filtering has become somewhat ineffective.

This is why intelligence-led detection – identifying numbers and ranges actively promoted for fraud – is now the only consistently effective prevention method.