The firm said it only became aware of the hack on Tuesday and quickly prevented the hackers gaining any more access, and notified affected customers.
“We immediately contained the risk and have been working with specialist advisors and taking appropriate steps to protect our customers and systems,” MAG said.
“We have informed and are working with the relevant authorities.”
The airport group said the e-mail addresses obtained by the hackers came from passengers signing up to the airports’ on-site wifi.
More detailed data, including vehicle registrations, came from people booking car-park spaces, arranging access to lounges, and booking fast-track.
Customers are urged to remain vigilant about suspicious emails, text messages or phone calls and avoid opening attachments from unknown contacts.
The identity of the hackers was known, MAG said, and the relevant authorities had been informed.