Many French candidates used a tool allowing them to 'match' information on voters (NationBuilder)

NationBuilder is an American political campaigning software company, which offers a fully integrated suite of tools for the organization of a campaign, and outreach through e-mail, telephone, social media, and traditional door-to-door campaigning. Many candidates in the 2017 French presidential elections were reported as using their services. Among others, the company offers a functionality called 'match'. When users provide their email address on a campaign's website, 'match' allows the harvesting of public data from their Facebook, LinkedIn, Twitter and other accounts. It further allows the integration to a candidate's database of every internet user who liked one of the candidate's Facebook or Twitter posts. This functionality was eventually deactivated as incompatible with CNIL's Guidelines on the collection of personal data from social media platforms. However, beyond the 'match' functionality, the company claims to be able to create action-focused websites, fundraise & process donations in minutes, target emails with social insights, and visualize paths to turn supporters into advocates. These actions may rely heavily on data processing to function and need to be carefully scrutinised and monitored.

Source: Report by TacticalTech and Judith Duportail "The 2017 Presidential Election: The arrival of targeted political speech in French politics"