KB107 - International Calling Tiers


Background: What problem are we trying to solve?

International call fraud is one of the largest issues plaguing the move from traditional, isolated communications systems to more open and interconnected IP-based systems. By allowing greater access to phone systems we are also exposing the system to those who would like to make a call on your dime. With this in mind, Clearfly attempts to mitigate financial exposure from multiple angles:

  • Allow the customer to explicitly block all international calls (Call Barring). International call barring is enabled by default on all new SIP trunks unless explicitly requested by the customer or partner.

  • Attempt to detect when the customer’s system is being used without their consent and block all future international calls to lessen the financial impact and give them time to secure their systems. Further details here.

Through these strategies Clearfly gives the customer the ability to flat-out prevent any risk of fraudulent international calls or, if the ability to place international calls is required, an automated system to reduce the financial impact of a fraudulent event. While these approaches have made a major impact in the amount of fraud our customers have been exposed to, there are still cases in which an attacker has been able to take control of a phone system and rack up a sizable bill before our fraud detection system notices a problem and blocks future international calls.

Going Further

Clearfly knows that there will be a subset of our customers that will always need to make international calls, precluding the use of international call barring. Many carriers have drawn a line in the sand and simply block all calls to "risky" countries. While this is a perfectly valid option, such an approach prevents customers from making legitimate calls to those locations. For example, calling certain countries in Africa might not be common for your organization, but several of our customers are international charities or travel agencies who make calls to far-flung corners of the globe on a daily basis. Wholesale blocking of certain country codes is simply not an option that would satisfy our diverse customer base.

Giving You the Choice

While one size doesn’t fit all, one size can usually fit most and by segregating international destinations into a few groups and allowing the customer to choose their calling tier we can minimize risk for the majority of our customers while still maintaining the flexibility to allow unrestricted international calling for customers with more diverse requirements.

Clearfly currently divides international destinations into three (3) distinct tiers (Viewable Here):

  • Tier 0: The most commonly called destinations (UK, Mexico, Japan, Germany, etc) and also the most reasonable to call in terms of per-minute rates. For this reason they are also uncommon targets for international call fraud. 86% of all international destinations fall into this tier.

  • Tier 1: Sightly more expensive rates and those which have a known history of infrequent fraud. Currently about 13% of destinations.

  • Tier 2: The most expensive and frequently targeted destinations for international fraud. Less than 2% of destinations fall into this tier and we estimate based upon our historical data that 95% of international fraud is destined for these locations. If you need to be able to call these destinations, please take extreme care when securing your system and keep in mind the importance of maintaining strong passwords.

Customers are able to call the highest tier for which they are subscribed as well as all tiers below. For example, Tier 2 customers can call 0, 1 and 2, while a customer subscribed to Tier 0 will only be able to call Tier 0 destinations.

Secure by Default

By default, Clearfly blocks (bars) international calling for all new voice services. If you need to be able to call internationally, call barring and international tier configuration can be updated by a customer or an authorized partner 24x7 via the Clearfly Portal.