Companies across the globe are reporting that they have been struck by a major ransomware cyber-attack.

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• Cyber-attack: Is my computer at risk?
• WannaCry: Your questions answered
• the Ukrainian central bank, the aircraft manufacturer Antonov, and two postal services
• Russia's biggest oil producer, Rosneft
• Danish shipping company Maersk, including its container shipping, oil, gas and drilling operations
• a Pennsylvania hospital operator, Heritage Valley Health System, which reported its computer network was down, causing operations to be delayed - but it is not yet clear if it was subject to the same type of attack
• Spanish food giant Mondelez - whose brands include Oreo and Toblerone - according to the country's media
• Netherlands-based shipping company TNT, which said some of its systems needed "remediation"
• French construction materials company St Gobain
• US pharmaceuticals-maker Merck and the local offices of the law firm DLA Piper - a sign in the firm's Washington DC office said: "Please remove all laptops from docking stations and keep turned off - no exceptions."