E.164 is the international telephone numbering standard established by the International Telecommunication Union (ITU-T).
Do Not Originate (DNO) is a designation applied to telephone numbers that should never be used to place outbound calls.
If a call appears to originate from a DNO-designated number, it is highly likely to be spoofed or fraudulent and should be blocked by the Communications Service Provider.
Communications providers and analytics platforms may use DNO data to help identify calls that warrant additional scrutiny as part of broader robocall mitigation efforts.
DNO programs are commonly used to protect telephone numbers that are not expected to originate voice traffic.
Examples may include:
A DNO designation does not prevent a number from receiving calls. Instead, it indicates that the number should not appear as the originating caller ID on outbound calls.
Caller ID spoofing remains a challenge across voice communications networks.
Many fraudulent calls attempt to impersonate trusted organizations by displaying telephone numbers that do not legitimately originate outbound calls.
Do Not Originate programs help identify these situations by establishing which numbers should never appear as the originating party on a call.
As part of broader robocall mitigation efforts, DNO data can provide an additional layer of intelligence for communications providers, enterprises, and analytics platforms.
Unused Numbers
Telephone numbers that are not currently assigned to customers generally should not generate outbound calls.
Inbound-Only Numbers
Many organizations maintain telephone numbers that are intended only to receive customer calls.
If those numbers suddenly appear as originating caller IDs, the activity may warrant investigation.
Government and Public Service Numbers
Certain public-facing numbers may be designated as non-originating to reduce opportunities for spoofing and impersonation.
Protected Enterprise Numbers
Businesses may identify specific numbers that should never be used for outbound communications and designate them accordingly.
Related topics include:
Organizations may identify specific telephone numbers that are not intended to place outbound calls.
These numbers can then be designated as Do Not Originate numbers.
Because legitimate outbound calling is not expected from these numbers, any originating call activity may be considered suspicious.
When a call enters a network, the originating telephone number may be compared against DNO data.
If the caller ID matches a DNO-designated number, the call may be:
The specific actions taken vary by communications provider and network environment.
DNO information is often used alongside other call authentication and analytics tools.
When combined with technologies such as STIR/SHAKEN and additional fraud intelligence, DNO data can help support efforts to identify suspicious calling activity.
DNO data can help identify situations where a caller ID appears to originate from a number that should not be placing calls.
Communications providers may incorporate DNO information into broader robocall mitigation strategies.
Organizations can help protect customer-facing telephone numbers from misuse by identifying numbers that should never originate calls.
DNO data can serve as one signal among many used to evaluate call activity and identify potentially suspicious behavior.
DNO information may complement authentication and validation technologies by providing additional context about expected calling behavior.
DNO stands for Do Not Originate.
A Do Not Originate number is a telephone number that should never be used to place outbound calls.
E.164 is the international numbering standard that defines phone number formatting. An MSISDN is the actual mobile phone number assigned to a subscriber.
Communications providers and analytics platforms may use DNO information as part of broader efforts to identify suspicious call activity and caller ID spoofing.
A DNO designation itself does not block calls. Providers determine how DNO information is used within their own analytics, validation, and mitigation processes.
Examples may include inbound-only numbers, unused numbers, customer service numbers, government service numbers, and other telephone numbers that should not originate outbound calls.
DNO and STIR/SHAKEN address different aspects of call trust. STIR/SHAKEN helps authenticate caller identity, while DNO data helps identify numbers that should not originate calls in the first place.
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