U.S. Secretary of Homeland Security Alejandro Mayorkas said on Tuesday that cyber threats facing the U.S. from hostile nations have never been greater or more complex, mentioning China, Russia and North Korea by name.

Mayorkas issued the assessment in a document before testifying before the House Committee on Homeland Security.

The secretary said the threats facing the U.S., from cyberattacks on critical infrastructure to increasing destabilizing efforts by hostile nation states, have never been greater or more complex.

He also said that cyber criminals and hostile nations such as Russia, China, Iran and North Korea are enhancing their cyber capabilities and producing more harmful results.

Mayorkas said that entities posing a digital threat to the U.S. have launched ransomware attacks with the intent to greatly disrupt daily life by targeting critical infrastructure, including financial institutions, hospitals, pipelines, electric grids and water treatment plans.