BlackCore is linked to activity in Angola, Togo and the 2025 mayoral election in New York, won by left wing candidate Zohran Mamdani, who is also a supporter of Palestine.
Viginum chief Marc-Antoine Brillant said it was still unclear who had commissioned BlackCore to interfere in France and other countries.
He added: "Our investigations did not make it possible to identify the sponsor or sponsors, if indeed they exist, behind this foreign digital interference."
French Prime Minister Sebastien Lecornu said the French government had asked Israel for an explanation on BlackCore's actions, but also for help trying to find out who may have been behind the smear campaign.
He said: "I do not doubt for a single instant that if a French private group, from French soil moreover, had engaged in foreign digital interference in Israel, they would have done the same to its ambassador on site."
BlackCore described itself as an "elite influence, cyber, and technology company built for the modern era of information warfare".
It said it provided governments and political campaigns with "cutting-edge strategies, advanced tools, and robust security to shape narratives."
The firm deleted its online presence after Reuters made inquiries.
Israel's embassy in Paris said it was waiting to receive details from the French probe before conducting its own investigation.
In a statement it said: "Israel has, of course, no intention to interfere in the French political process, be it at the national or municipal level."