Websites from the Gendarmerie (French police)
Pharos: This is the web site from the French home office dedicated to reporting crimes that you have witnessed. When you click on “report a crime”, you can choose from different sections between Terrorism, pedophilia, slavery, fraud, endangering people, cruelty to animals or scams. When you click on the one you want to report, it explains how to do it and directs you to the relevant site or form to fill in. Some crimes can be reported anonymously.
https://www.internet-signalement.gouv.fr/PharosS1/
For the scams, you can simply do a screen shot of the scam you receive and send it to the authorities.
Online fraud: This is a web site to give you advice if you think you have been a victim of online fraud or are subject to extortion. There are also loads of useful tips to protect yourself against online scams.
On this site, you can chat to a Gendarme straight away so he can advise you on what to do next to protect yourself.
Ma securité: This is the official web site of the French Police/Gendarmerie on which you can fill in a police report online, but you can also chat anonymously to a police official about your query (as long as it is about crime) to find out if it is worth reporting for instance.
www.masecurite.interieur.gouv.fr
It also gives you the addresses of all the police and Gendarme stations so you can find the one closest to you.