French regulator seeks to trace the origins and routing of fraudulent calls amid growing evidence that existing authentication measures are being circumvented
France’s telecoms regulator Arcep has opened a broad administrative enquiry into operators that assign numbers from the national numbering plan, as it steps up efforts to tackle persistent caller ID spoofing and scam calls. The move follows a sharp rise in complaints submitted to the regulator’s “J’alerte l’Arcep” reporting platform. According to Arcep, reports of number spoofing increased from just 531 in 2023 to more than 19,000 in 2025, making it the most frequently reported consumer issue received by the authority.
The regulator says the scale and seriousness of these reports demonstrate that fraudulent actors continue to find ways around legal and technical safeguards designed to prevent misuse of telephone numbers.
Victims of spoofing typically discover that their own phone number has been hijacked and displayed as the caller ID for scam or spam calls. Many report receiving angry or distressed calls from people who believe they have been contacted for fraudulent or unsolicited purposes. In more serious cases, fraudsters have displayed the numbers of government bodies or financial institutions to lend credibility to their scams, further undermining trust in voice communications.
Locating the source
Arcep’s enquiry is intended to establish how such calls are originating and how they are being routed across interconnected networks, as well as to verify whether operators are complying with their legal obligations on caller ID authentication. Given the complexity of interconnection arrangements and the number of parties potentially involved in carrying a single call, the investigation has been opened into all operators authorised to assign numbers from France’s national numbering plan.
The regulatory action builds on a framework introduced under the Law of 24 July 2020, which requires operators to authenticate caller IDs and to block calls whose numbers cannot be properly verified. In practice, this relies on a “chain of trust” between operators, with authentication information attached by the originating network and passed along the call route. Widespread deployment of this mechanism began in October 2024, with further obligations applying to mobile networks from January 2025.
More recently, Arcep amended the national numbering plan rules to address risks associated with international traffic. From 1 January 2026, operators are required to mask French mobile numbers on incoming international calls where authentication cannot be confirmed, rather than allowing unauthenticated calls to be completed. The regulator argues that this measure is necessary to counter a common fraud technique in which calls originate abroad but present a French mobile number as the caller ID.
Ongoing weaknesses
Despite these steps, Arcep notes that the volume of complaints suggests ongoing weaknesses in the application of authentication rules. In its decision to open the enquiry, the authority highlights the possibility that some calls may be improperly authenticated at source, or that unauthenticated calls are not being interrupted as required while transiting or terminating on networks.
As part of the investigation, Arcep’s agents are empowered to request documents and technical information from operators and their subcontractors, including partners involved in implementing authentication systems. The regulator said it may also carry out on-site inspections where necessary. The objective is to reconstruct the paths taken by suspect calls, identify the operators involved at each stage, and assess compliance with obligations set out in the postal and electronic communications code and related Arcep decisions.
The enquiry reflects growing concern among regulators that caller ID spoofing poses a systemic risk to consumer confidence in voice services. Arcep said the investigation is a necessary step to ensure effective enforcement of existing rules, rather than the introduction of new regulatory measures, but its findings could have significant implications for operators found to be falling short of their responsibilities. This however carries little political flack because the practice is despised by the general public.
