Macron is due to land in the French overseas territory in the Pacific on Thursday after government electoral reforms passed a week ago sparked riots that have killed six people. Some leaders fear the change will dilute the vote of indigenous Kanak, who make up 40% of the population.
The New Caledonia government said a large cyberattack launched soon after the announcement of Macron's visit had aimed to make internet services unavailable, with millions of emails sent to one address.
The attack had been stopped and its origin was unknown, an official said in a livestreamed press conference on Wednesday.
France's High Commission said Macron would be accompanied by ministers for defense and interior for Thursday's talks, and some 100 members of the GIGN or elite tactical response group were deployed in New Caledonia.
More than 1,000 security reinforcements from France were on the ground, some 90 barricades had been cleared from roads, and the night had been calmer despite two fires in Noumea, the high commission said on Wednesday. Some 20 arrests were made on Tuesday, with 280 rioters arrested in the past week.
Macron will meet elected officials and local representatives on Thursday for a day of talks focused on politics and on the reconstruction of the island, Reuters reported.
France annexed New Caledonia in 1853 and gave the colony the status of overseas territory in 1946. New Caledonia is the world's No. 3 nickel miner but the sector is in crisis and one-in-five residents live below the poverty threshold.
The island is more than 16,000 km (10,000 miles) from mainland France, and some 1,500 km (930 miles) east of Australia.