SIP trunk fraud, in which hackers gain control of an organization’s SIP trunk and make unauthorized calls, is becoming more common, and it’s often difficult to detect since call patterns can look similar to normal usage. Businesses need to take measures to avoid scenarios such as:
  1. Calls placed to high-risk premium destinations
  2. Overnight loss of credits
  3. Calls placed from your account to unknown numbers, leading to unintended consequences
Zentrunk Geo Permissions lets Plivo SIP trunk users selectively enable or disable outbound calling to international destinations. Doing so helps organizations avoid calls to high-cost routes and prevent other fraudulent activities.

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Outbound SIP trunk geo preferences

You can restrict the list of countries to which users can place calls through Zentrunk. To do this, on the Plivo console, navigate to Zentrunk > Geo Permissions. Placing a country-level block: By default, calling to all countries is allowed. You can deselect specific countries, then click Save Changes. The new country restrictions go into effect immediately. Zentrunk will not allow calls to countries that are deselected.
In the example above, calls to Spain, Sweden, and Switzerland are allowed. Calling to other countries on the list is barred. Placing a high-risk voice network group block: Plivo analyzes call trends and rates of premium voice network groups for each country. We maintain a list of high-risk voice network groups. You can block calls to these groups by clicking on High Risk Permissions and making sure the toggle is Enabled, as it is by default, then clicking Save Changes. From that point on, outbound calls to preidentified risky prefix clusters are blocked. Plivo periodically updates the list of high-risk groups.

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Geo permissions disabled by Plivo

Plivo analyzes call trends and disables geo permissions when we discover suspicious activity toward any country. You might see a “Disabled by Plivo’” tag for a country or a message saying “Please contact Plivo support to re-enable geo permissions for any country that’s disabled below.” This indicates that Plivo has identified suspicious activity and disabled the geo permissions to avoid calls getting placed from your account to unknown numbers and destinations. To unblock geo permissions in such instances, contact Plivo support.
These response codes will show in your call detail report if geo permissions are disabled: SIP Response Code: 403 - Barred Country; Zentrunk Hangup Code: 4650 Description: The number has been blocked in geo permissions settings. Any calls made to this number belong to a specific country or number group will not go through since it has been barred.

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Calls to blocked countries

If a call is placed to a destination number that belongs to a country that has not been selected in Geo Permissions, these response codes will show in your call detail report: SIP Response Code: 403 - Barred Country; Zentrunk Hangup Code: 4650 Description: The number has been blocked in geo permissions settings. Any calls made to this number belong to a specific country or number group and will not go through since it has been barred.