by Jessica Lindelöf, Product Director – Watchdog Fraud Management Solutions

Telecommunications fraud is a widespread and diverse global challenge, damaging operator and service provider reputations and relationships with their subscribers.


While fraudsters are well known for their malicious innovations, they are loyal to what works; once a scamming method proves to deliver dependable results, they relentlessly take advantage over the long term. One tried and true scamming workhorse stands out from the crowd for its longevity, fraudulent profitability, and negative impact on subscribers: Wangiri, otherwise known as callback fraud, is often the revenue generating part of International Revenue Sharing Fraud (IRSF) schemes.

‘Wangiri’ loosely translates to one ring cut in Japanese. Fraudsters call a target list and avoid call completion fees by hanging up before subscribers answer. The missed call prompts some subscribers to call the number back. Subscribers’ callbacks are then re-routed to an International Premium Rate Number (IPRN) or other number charged at exorbitant fees, where they are encouraged to wait on hold. This results in significant international billable time on the line, which the fraudsters then pocket as revenue.

Although this type of fraud has been around for over a decade, there is no sign of it going away – rather the opposite. Wangiri attacks continue to occur in all corners of the globe, creating a major source of fraudulent and billable traffic. The Communications Fraud Control Association (CFCA) reported in their 2017 survey that IRSF is the top fraud type, generating $6.1 billion USD in fraud revenue.

The fraudulent calls can be made from anywhere in the world, but seem to usually originate from countries that are far away in relation to the called subscriber’s home network from un-allocated numbers or from numbers reserved for satellite telephone carriers.

News reports on countries with fraudulent call origin have included Belgium, Chad, The Cook Islands, Estonia, Grenada, Libya, Nigeria, Pakistan, Papua New Guinea, and Switzerland, among others. The diverse geographic distribution of fraudulent activity origin, massive subscriber reach, and rapid, dependable payoff for fraudsters highlights the need for international Fraud Management solutions to prevent malicious incentives.

These attacks are performed by coordinated teams of ‘Wangiri callers,’ who initiate the scam interaction utilizing autodialing technology capable of thousands of calls a minute, and ‘content providers,’ who receive the re-routed callbacks and filibuster subscribers’ time to keep them on the line.

The autodialer issues very short calls that often do not generate Call Detail Records (CDRs), which increases attack stealth and the number of impacted subscribers. It only takes a small percentage of victims that call back to generate thousands of dollars in a single day. The next day, they set up a new number and subscriber target list, with many subscribers targeted in multiple fraud campaigns. These international fraud teams then share the generated revenue.

Subscribers’ bill shock and vulnerability to this scam negatively impacts their customer experience, and can spur a chain of reactions – damage to their service provider’s reputation, loss of confidence and satisfaction with services rendered, decrease in additional services purchased, and the potential for churn.

What can Operators do to detect and protect against Wangiri?

  1. Detect the incoming Wangiri calls, those that entice the subscribers to call back:
    • Monitor incoming calls from high risk countries
    • Monitor large numbers of incoming very short or unanswered calls
    • Customer complaints about calls from unknown international numbers
  2. Detect Wangiri callback calls:
    • Monitor outgoing calls from many subscribers to international numbers with unfamiliar or high risk country codes
  3. Take precaution:
    • Inform and warn subscribers
    • Maintain updated blacklist of known fraudulent numbers, especially in high risk countries
    • Route calls to suspected, high risk countries to a pre-call announcement, informing customers about the risk and cost
  4. Prevention:
    • Block incoming calls from known Wangiri number ranges
    • Block outgoing calls to known Wangiri number ranges
    • Time is critical – aim at stopping known and suspected fraud calls as early as possible, through:
      • Automation
      • Real-time signalling


The Enghouse Networks WRM Watchdog Fraud Management system is a comprehensive, turn-key end-to-end solution that effectively detects and combats fraud. Watchdog identifies and prevents Wangiri fraud through automated and customizable configurations to detect specific patterns and alert the fraud management team. When certainty about the fraud is established, Watchdog can enable blocking of the Wangiri phishing calls, numbers or subscribers.

Want to know more? Download our Watchdog product sheet.
Questions? Jessica Lindelöf, Product Director, has your answers.