Protect Unassigned Numbers from Fraud

Identify and protect unassigned number inventory as Do Not Originate (DNO) to reduce spoofing, strengthen trust and support industry-wide fraud mitigation.

The Missing Signal in Robocall Prevention

Telephone numbers allocated to a service provider but not yet assigned to an end user can create an opportunity for misuse.

Bad actors can spoof these numbers to make fraudulent calls appear legitimate, potentially exposing consumers to fraud before a number ever reaches its intended end user.

Local Service providers need a reliable way to identify and protect unassigned number inventory that should not originate calls.

You can’t stop spoofing of unassigned numbers if networks don’t know which numbers should never originate calls.

Understanding Telephone Number Status

Not all telephone numbers are in the same stage of their lifecycle. Understanding the differences between unused, unassigned and unallocated numbers helps service providers better manage number inventory and protect telephone numbers before they are assigned to an end user.

Unassigned Numbers
Local telephone numbers that have been allocated to a service provider but have not yet been assigned to an end user. These numbers represent unassigned number inventory and can be protected through DNO until they are activated.

Unallocated Numbers
Numbering resources that remain under NANPA administration and have not yet been allocated to a service provider.
Because these numbers have not been assigned to a provider, they remain outside of provider-managed inventory.

Simple. Scalable. Trusted.

Helping service providers identify and protect unassigned number inventory while supporting a more trusted communications ecosystem.

Identify Unassigned Number Inventory

Identify unused and unassigned telephone numbers that should not originate calls.

Contribute DNO Data

Submit unassigned number inventory through RealNumber’s trusted framework and designate those numbers as DNO until they are assigned.

Enable Smarter Blocking

Give downstream providers, analytics platforms and enterprises actionable DNO intelligence to help identify calls originating from numbers that should not be in use.

RealNumber DNO Inventory Use Cases

Protect unassigned number inventory at different stages of the number lifecycle.

Newly Allocated Number Blocks
Protect telephone numbers within newly allocated 1,000-number blocks while they remain unassigned to end users.

Unassigned Inventory
Designate telephone numbers that are part of a provider’s inventory but have not yet been assigned to an end user as DNO until activation.

Returned or Recycled Numbers
Protect telephone numbers that are no longer in active service and are awaiting reassignment to another end user.

Inventory Lifecycle Management
Maintain DNO status as number inventory changes, adding protection when numbers are unassigned and updating their status when they are placed into service.

Introduce Greater Trust with RealNumber® DNO Inventory

RealNumber® Do Not Originate (DNO) enables Resp Orgs, Service Provider ID (SPID) owners and Operating Company Number (OCNs) to proactively identify numbers as DNO, helping the ecosystem recognize and block unauthorized traffic before it reaches consumers.

By contributing DNO inventory data, you help create a stronger foundation for:

Robocall mitigation and fraud prevention
Reduced spoofing of inactive or unused numbers
Improved network integrity and trust
More accurate analytics and call treatment decisions
Industry-wide collaboration against fraudulent traffic

Introduce Greater Trust with RealNumber® DNO Inventory

Built for a More Trusted Calling Ecosystem

Trusted Contributor Framework

Establish a trusted framework for identifying and validating DNO inventory contributed by authorized industry participants, improving confidence in shared data while supporting more accurate fraud prevention and call authentication efforts.

Scalable Participation

Designed for SPID and OCN holders managing large numbering inventories, enabling organizations to designate unassigned numbers as DNO and protect them from spoofing and misuse until they are assigned to an end user.

Actionable Intelligence

Deliver trusted number intelligence that supports call blocking, analytics, fraud detection and operational workflows, helping service providers make more informed decisions and strengthen protections across the communications ecosystem.

Ecosystem Collaboration

Foster industry-wide collaboration by enabling trusted organizations to share DNO inventory information, strengthening collective efforts to combat spoofing, illegal robocalls and other communications fraud targeting consumers and businesses.

Trusted Framework Participation Intelligence Collaboration

Frequently Asked Questions About Unassigned Number Inventory

Unassigned Number Inventory

What is unassigned number inventory?

Unassigned number inventory includes telephone numbers that have been allocated to a service provider but have not yet been assigned to an end user. Because these numbers are not in active use, they should not be originating calls.

Why should service providers protect unassigned telephone numbers?

Unassigned telephone numbers can be spoofed by bad actors and used to make fraudulent calls appear legitimate. Identifying these numbers as DNO helps signal that calls originating from them should not be trusted, reducing opportunities for spoofing and helping protect consumers from fraud.

How can service providers protect unassigned numbers in 1,000-number blocks?

Service providers may receive numbering resources in blocks of 1,000 telephone numbers before every number has been assigned to an end user. Providers can add the unassigned numbers within those blocks to DNO, indicating that they should not originate calls until they are placed into service.

What happens when an unassigned telephone number is assigned to an end user?

When a telephone number is assigned to an end user and placed into service, the provider can update its inventory and remove the number from DNO. Keeping DNO status aligned with assignment status helps maintain accurate number intelligence throughout the telephone number lifecycle.

How does DNO help prevent spoofing of unassigned numbers?

DNO provides an authoritative signal that a telephone number should not be originating calls. By contributing unassigned number inventory to DNO, service providers give downstream providers and other ecosystem participants actionable intelligence that can help identify and block calls spoofing numbers that are not yet in service.

What are the benefits of managing unassigned number inventory with DNO?

Proactively managing unassigned number inventory with DNO helps service providers protect numbers before activation, reduce opportunities for number spoofing and contribute trusted intelligence that supports fraud mitigation across the communications ecosystem.

Help Stop Number Spoofing Before Assignment

RealNumber DNO helps service providers proactively protect unassigned number inventory before it reaches an end user, creating stronger signals for fraud prevention and more trusted communications.

To learn more, schedule a demo today!

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