ransomware

The company has declined to provide detail on the nature of the attack, but moving systems offline is often a response to ransomware attacks.

One of the best examples is ransomware, malicious software that prevents users from accessing their computer files, systems or networks unless they pay a ransom.

Trump seemed to be giving Putin "a free pass as Russia continues to launch cyberoperations and ransomware attacks against critical American infrastructure", Schumer added.

Three years before, Russian ransomware attackers shut down the Irish health system's entire computer network, and published 520 people's medical records online.

A school in Cheshire has announced a temporary closure after falling victim to a "ransomware attack".