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Perhaps it is simply curiosity, or the fear of missing out on something, that provokes us to respond to or return missed calls on our phones - even when we don’t recognise the number.

If your phone rings just once, the caller hangs up and you don’t recognise the number it’s very likely to be the start of a fraud. If you make the simple mistake of calling back, as millions do, you will be routed via some far-flung destination to a premium rate number that plays you a pre-recorded message and charges you an exorbitant fee for the privilege.

The process works like this: the fraudster, or scammer, places a wide number of calls, via an automated dialler, to a disperse series of numbers and hangs up after one or two rings. They may call back several times. The idea is to get the target (or victim) to call the number back. When they do, they will likely be charged long distance fees to connect the call, and/or be charged for premium rate fees that are usually paid in part to the fraudster.

This type of fraud, commonly known as Wangiri (Japanese for “one ring and drop”), has been around since 2013 and despite efforts of telecoms companies to educate customers and the introduction of methods to prevent such calls, it has continued to grow. This year alone, the USA has reported a 98% increase in the first quarter (as compared to Q4 2018), and has more recently seen a massive spike in calls originating from West Africa’s Sierra Leone.

It is difficult for telcos to do a lot in these situations. Recognising the network the calls are emanating from is easy but blocking all incoming and outgoing calls to that particular network is simply not an option. Working with interconnect partners internationally to block all incoming and outgoing calls to recognised Wangiri phone numbers is a better option but the fraudsters simply move to new numbers when this happens. In some cases, the network terminating the calls may even ‘turn a blind eye’ to capitalize on the new revenue stream themselves or because internal staff are working with the fraudsters.

Fraud management systems are becoming more sophisticated in detecting and stopping Wangiri by utilizing new technologies such as machine learning and artificial intelligence.

The solution, based on Home Policy, looks at all incoming calls into the network (Fixed and Mobile Interconnect) and checks the following:

1. If the Calling Number is in an unallocated range, a policy decides if the call should be blocked or allowed (as these could also be CLI Refiling calls or marketing calls).

2. If the Calling Number is a known premium number a policy decides what to do with it. Typically, these are Wangiri numbers and would be blocked.

3. If the Calling Number has originated more than X number of calls in a specified time period, and if the calls are missed call or short duration call, the numbers are blocked or future calls are routed to an IVR.

4. If a range of numbers making Wangiri calls is recognised using an in-built list of Fraudulent Premium Rate Numbers.

There are other checks to identify Refiled calls, Caller ID Spoofing, Early Answer Fraud, etc. however, in the case of Wangiri calls, they need to be blocked in real time. 

But it’s not just about voice calls. As fraudsters become more ‘sophisticated’ we are now seeing cases where incoming SMS messages contain numbers to call back that are IRSF (Internal Revenue Share Fraud) numbers or are in the unallocated range that has been ‘hijacked’ from an interconnect carrier and billed at a premium rate.

With Caller ID Spoofing, an on-net caller can also spoof foreign premium rate numbers or send SMS messages with foreign numbers in them. Simply monitoring interconnects will miss these, but even though the current rate of such incidents from on-net is low it still needs to be included.

The machine-learning mechanisms mentioned earlier now enable the identification of patterns for numbers at the time of the attack which may not even be listed yet. Wangiri affects customers of mobile and fixed line operators around the globe and Mobileum is working with a number of different operators to restrain Wangiri fraud levels even further. 

If you want to know more, please contact us.

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