Several of Europe's biggest airports still faced disruptions on Monday after hackers knocked out automated check-in systems provided by Collins Aerospace, owned by RTX, affecting dozens of flights and thousands of passengers since Friday.
"Law enforcement is involved to investigate" malicious software that locks up data until the victim pays to have access restored, the ENISA agency said in Monday, without saying where the ransomware attack originated from.
Governments and companies have been the targets of cyberattacks in recent months, including luxury car maker Jaguar Land Rover, which had to pause production as a result.
Rafe Pilling, director of threat intelligence at British cybersecurity firm Sophos, said there have been more ransomware attempts targeting higher-profile victims because of the attention they brought, but such attacks were not becoming more frequent.
"Disruptive attacks are becoming more visible in Europe, but visibility doesn't necessarily equal frequency," he told Reuters.
"Truly large-scale, disruptive attacks that spill into the physical world remain the exception rather than the rule."
A survey of some 1000 companies by German industry group Bitkom found that ransomware - malicious software that locks up data until the victim pays to have access restored - was the most common form of cyberattack, with one in seven companies having paid a ransom.
Collins Aerospace said on Monday that it was working with the affected airports, including Brussels and London Heathrow, Europe's busiest airport, and was in the final stages of completing updates to help restore full functionality.
Berlin airport, which was facing higher passenger numbers than usual on Monday due to the Berlin Marathon, still did not have its check-in systems restored and reported delays of over an hour for departures.
One passenger described the boarding process as akin to the early decades of commercial air travel, with handwritten boarding passes.
Brussels Airport was using iPads and laptops to check passengers in online, with 60 out of roughly 550 departing and arriving flights being cancelled on Monday.
Dublin Airport was experiencing "minimal impact" and had some manual processes in place.
