The Decision being published today aims to improve the caller ID authentication mechanism by preventing number spoofing. It also factors in the new provisions of the Law of 30 June 2025 to combat public aid fraud. Most of these measures will enter into force on 1 January 2026.
18,000 reports of number spoofing logged on the “J’alerte l’Arcep” user reporting platform since January 2025: crucial increased protection to curb caller ID spoofing
The Law of 24 July 2020 on supervising telemarketing and combatting fraudulent calls[1] provided for the implementation by operators of a caller ID authentication mechanism, whose technical specifications were established by French telecoms operators. This mechanism, which is currently being used by virtually every operator in France, requires them to cut off all non-authenticated calls, and forward the information for identifying a call’s originating operator. This traceability, combined with operators’ cooperation, creates the ability to identify the origin of fraudulent calls, after the fact.
Despite which, Arcep has received close to 18,000 reports of number spoofing on its “J’alerte l’Arcep” user reporting platform since January 2025. The sheer number of these reports proves that scam call perpetrators have found ways to circumvent the authentication obligation and spoof telephone numbers, especially mobile ones. Even if they are often short-lived, these spoofing incidents are a source of legitimate concern for the subscribers whose number has been used for fraudulent ends; and they are regularly contacted by people who are upset about having been the target of the calls.
In the Decision being published today, and in light of the responses to the public consultation held from late July to late September 2025, Arcep plans to take action on three fronts:
Display “No caller ID” when an international call using a French mobile number could not be authenticated. A very large number of scam calls using a spoofed mobile number are made from abroad to people in France without being filtered, as French operators are not always able to distinguish legitimate calls being made by French subscribers who are travelling abroad (i.e. roaming). While operators now have technical protocols enabling them to ensure the authenticity of a subscriber’s number while in roaming, the transition to these protocols is gradual. At the end of 2025, more than 80% of calls from roaming French subscribers were authenticated by these protocols. Once the transition is complete, all of French subscribers’ roaming calls will necessarily be authenticated, at which point operators will be able to distinguish between roaming calls being made by their subscribers and international calls that have spoofed a mobile number.
During the transition, however, both legitimate and illegitimate calls from abroad with non-authenticated mobile numbers will continue to cohabitate. To increase trust in the caller ID being displayed on subscribers’ phones, and to protect mobile customers from attempts to spoof their number, Arcep is asking operators to mask (i.e. display “No caller ID”) the non-authenticated mobile number on calls coming from abroad. As a result “No caller ID” will mean either that the caller wanted to mask their phone number, or that the caller ID could not be authenticated for technical reasons, in other words without prejudging the legitimate or fraudulent nature of the call. This measure will increase call recipients’ ability to trust the caller ID numbers displayed. It will come into effect on 1 January 2026, except in the territory of Saint Martin where, due to particular local conditions and existing roaming agreements, its application will be postponed until 1 January 2028.
- Recommend that operators display “No caller ID” in those instances where technical restrictions prevent them from relaying caller ID authentication information when routing the call. Either because it is old or suffers from technical limitations, some calling equipment may not always be capable of properly relaying number authentication data when rerouting calls. These weaknesses can be exploited by experienced fraudsters. Arcep recommends that, in these instances as well, operators mask (i.e. display “No caller ID”) the caller’s number to avoid potentially legitimate calls from being interrupted by the call recipients’ operators, while also reducing the risks of spoofing. Operators must nevertheless preserve the original call’s signature, document the technical reasons for masking the caller ID, and inform Arcep of the actions taken to remedy the technical issues that led to the caller ID alteration.
- Clarify the obligation imposed on call origination operators to verify caller ID numbers used by their customers. The number authentication mechanism relies on a “chain of trust” between operators, which is based on verification performed by the operator on whose network the call originates. That operator must verify that its customer is duly authorised to use the number they want to employ as their caller ID. To guarantee this systematic verification, Arcep will require operators to define the list of numbers that the customer can use as their caller ID in that customer’s service contract, and to restrict by technical means the numbers that the customer can use when calling to only those numbers on the list.
Create a category of numbers for calls and messages that serve a general interest objective
Article 16 of the Law to combat public aid fraud[2] mandates Arcep to define numbers “dedicated to calls and messages serving a general interest objective” made by automated systems. These numbers can only be assigned to the organisations included on a list set by joint order of the ministers responsible for consumer affairs and for electronic communications. To this end, Arcep is creating a number category for calls and messages serving a general interest objective that are made by automated call systems, and is establishing the rules governing their use by those organisations previously designated by the ministerial order.
Improve the efficiency of French Overseas number management to satisfy the needs of businesses and consumers
In response to growing demand for numbering resources, particularly to meet the needs of new use cases, Arcep is introducing a series of measures designed to achieve more efficient management of these numbering resources, which include the assignment of new ranges of numbers to certain Overseas territories.
Lastly, Arcep is also introducing new measures designed to increase consumer protection. As a result, Arcep is requiring operators to freeze the reassignment of a telephone number to another user for a minimum 45 days after that number has been cancelled at the operator’s initiative, for instance following the decommissioning of a copper network access line, giving the initial user the ability to request the recovery of their cancelled number before it is reassigned to another user. These changes come in response to requests that operators have made to Arcep, and to user reports submitted via the “J’alerte l’Arcep” site.
Associated documents
- Decision No. 2025-2215 amending the Decision establishing the national numbering plan and its management rules (pdf - 1.68 MB)
- Contributions to the public consultation (zip - 8.84 MB)
To find out more:
“Numbering” Key issue page on the Arcep website: main laws and regulations, history of Arcep decisions, number portability and directory services