Why a classic spam filter is no longer enough

A classic telephone spam filter compares the incoming number to lists: black list of reported numbers, list of opposition to canvassing (Bloctel), prefixes reserved for commercial canvassing. This approach works against mass telemarketing, which reuses the same numbers for a long time. It fails against targeted fraud, which changes numbers at will, spoofs legitimate numbers and relies on conversation — not call volume — to deceive its victim.

Why list blocking fails, point by point

1. 1
   Numbers are disposable

   A number costs a few cents and activates online in a few minutes. By the time a number is reported by victims, blacklisted and distributed to blocking applications, the fraudster has already abandoned it for the next one. The blacklist describes the past; the scam is always one number ahead.

2. 2
   Spoofing turns the filter against you

   Number theft allows you to display an identifier that is not yours — that of your bank, an administration, a loved one. The list filter then lets the call go through precisely because the number displayed is deemed safe. The number authentication mechanism deployed in France since October 2024 complicates the exercise on landlines, but does not eliminate it: mobiles, international calls and leased numbers remain usable.

3. 3
   Bloctel only stops the honest

   Bloctel is a list opposing canvassing commercial : legitimate companies must respect it under penalty of sanction (DGCCRF). Scammers obviously do not consult it. Registering remains useful - it reduces the noise of legal canvassing - but it does not filter out any scam attempts.

4. 4
   Total blocking isolates — so it's disabled

   The radical option — blocking all unknown numbers — also cuts off the doctor who calls back, the laboratory, the delivery person, the town hall. For an older person, these calls matter. Result observed: the total blocking ends up deactivated at the first important missed call, and the line is left without any protection.

5. 5
   The danger is not in the number, it is in the conversation

   A fake bank advisor or a progressive manipulation are not recognized by any prefix. What gives them away is the content: the manufactured urgency, the request for code, the required secrecy, the emotional pressure. No number list can detect this — only analysis of the call itself can.

Filter by list or call analysis: comparison

What really protects a line today

Good tools overlap — none replaces the others:

1. Keep a basic filter and Bloctel. They reduce the volume of legal canvassing and massive campaigns already reported — bloctel.gouv.fr, free.
2. Establish a family reminder reflex. Any sensitive request by telephone = hang up and call the organization back yourself at its official number. This reflex alone defuses most scenarios.
3. Report systematically fraudulent numbers 33700 : each report accelerates the blocking of current campaigns for everyone.
4. For a vulnerable person, add analysis of the conversation. This is the layer that filters are missing: an assistant that responds to strangers, verifies identity and reason, and monitors for scam signals during the call — see how Kin-Guard works.

What Kin-Guard does differently

Kin-Guard does not judge a call by its number, but by its content. The assistant answers unknown calls in place of your loved one, asks who is calling and why, lets legitimate calls through without friction – doctor, pharmacy, craftsman – and keeps fraud scenarios at bay, even from a new or spoofed number. And because some fraudsters only reveal themselves during a conversation, surveillance continues during the call. It's the difference between reading the label and opening the letter.

Frequently asked questions

Article written by Charlie BART, founder of Kin-Guard. Published on July 7, 2026.

Sources: Bloctel — List of opposition to telephone canvassing · ARCEP — Number authentication (anti-spoofing plan) · Cybermalveillance.gouv.fr

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