Printers and copiers could be the weak link in many corporate cyber defenses, the European Union’s information security agency warned Tuesday.

The EU said companies are often unaware of the dangers posed by printers that are connected to the Internet, which can serve as conduits to penetrate networks or a window to stored documents.

The European Network and Information Security Agency also advised companies to take physical security precautions for their printers and copiers to prevent unauthorized access to documents or data cartridges.

“Business in Europe must realize that printing and copying is not as safe as when Gutenberg started printing 540 years ago,” said Andrea Pirotti, executive director of the agency. “Crucial company assets and confidential data” are at stake as even printers can get “hijacked, he said.

The agency surveyed 350 companies in France, Germany and Britain.