Expert Says 15% of IRSF Sent to B-Numbers Too Long or Too Short to Be Valid

The global telecoms industry does a great job of connecting people, with the result that the near perfect completeness of the interconnected network is largely taken for granted. However, telcos also make connections when none should be allowed. Those seeking to reduce International Revenue Share Fraud (IRSF) will sometimes advocate the blocking of all calls to an entire country if it is considered a risky destination. But why are we using such crude techniques that also prevent legitimate international calls when we simultaneously fail to apply the basic intelligence that would distinguish a real phone number from one which cannot be legitimate because the number of digits is wrong? Dial plan expert Guy Howie recently observed:

…around 15% of calls made during IRSF attacks are to B numbers with an invalid digit string length. The B numbers lengths of such calls are all shorter or longer than specified by the National Regulator. This is an immediate giveaway that the calls are invalid and fraudulent.

We use computers. Are we seriously going to pretend that checking if a dialed number has a digit too many, or a digit too few, is beyond our capabilities? Howie explained how the necessary information is available – but that many telcos remain ignorant of it.

One important attribute, which nobody seems to talk about very much, is the Digit String Length of IRSF calls. In the world of telephony, fixed A and B number Digit String Lengths are critical to the successful allocation of phone numbers and termination of calls. Whilst the valid lengths of different call types are quite complex, they are documented by National Regulators in their National Number Plans. When we used these documents and databases to help create the database of International Unallocated Destinations, we also decided to collate valid digit string lengths to help the industry combat IRSF.

Some parts of the world are more prone to calls involving numbers that are of invalid length.

We’ve observed much higher percentages of invalid digit string length calls to certain destinations in Liberia and Somalia, where some fraudulent routes appear very well established. It never ceases to amaze us that we keep seeing frauds to these same destinations.

In 2017 the CFCA estimated that IRSF was worth USD6.1bn globally. A 15 percent reduction would be worth almost a billion dollars. If simple checks regarding the length of phone numbers would be sufficient to eradicate 15 percent of IRSF, then our industry has no excuse to block entire countries whilst we fail to count the number of digits being dialed.

Eric Priezkalns
Eric Priezkalns
Eric is the Editor of Commsrisk. Look here for more about the history of Commsrisk and the role played by Eric.

Eric is also the Chief Executive of the Risk & Assurance Group (RAG), a global association of professionals working in risk management and business assurance for communications providers.

Previously Eric was Director of Risk Management for Qatar Telecom and he has worked with Cable & Wireless, T‑Mobile, Sky, Worldcom and other telcos. He was lead author of Revenue Assurance: Expert Opinions for Communications Providers, published by CRC Press. He is a qualified chartered accountant, with degrees in information systems, and in mathematics and philosophy.