Airbus SE said it has taken steps to shield itself from cyberattacks targeting the European aerospace and defense company through subcontractors’ computer systems.

The maker of passenger planes and military jets is aware of cyber events and has detection methods to respond quickly, a spokesman said last week. Rolls-Royce Holdings Plc and France’s Expleo are among four Airbus suppliers targeted, possibly from China, over the past year, Agence France-Presse reported earlier.

The attempts to gain entry into Airbus’s computer systems isn’t the first time the Toulouse, France-based company has confirmed being a target. In January, it said it reinforced security after a cyber breach at its jetliner business allowed hackers to access some employees’ personal information. Rival Boeing Co. was hit last year.

The attacks targeting Airbus have prompted French authorities to order strategic companies to bolster their security arrangements with trusted partners and suppliers, according to a person familiar with the matter.

Airbus is one of about 200 entities on a list of so-called “vital operators” that are considered of strategic importance by the country’s national security agency. Airbus may have left an opening for hackers by failing to ensure suppliers are properly protected, said the person, who declined to be named because the information isn’t public.

“As a major high tech and industrial player, Airbus is like any other company, a target for malicious actors,” the company said Thursday. “Airbus continuously monitors activities on its systems, has detection mechanisms in place, and takes immediate and appropriate actions when needed.”

A spokesperson for Rolls-Royce said the company doesn’t comment on reports of individual attempts to gain access to its systems and works with authorities to combat any.