A huge extortion cyber-attack hit dozens of countries yesterday, holding computer data for ransom at hospitals, telecommunications firms and other companies. <br/><br/>Computers in thousands of locations were locked by a programme that demands equivalent of 300 US dollars to unlock the systems. According to reports, the attack used tools believed to have been developed by the US National Security Agency.<br/><br/>The attack hit Britain's health service, forcing affected hospitals to close wards and emergency rooms. Hospitals in areas across Britain found themselves without access to their computers or phone systems. Most of the affected hospitals were in England, but several facilities in Scotland also reported being hit.<br/><br/>British Prime Minister Theresa May said there was no evidence that patient data had been compromised in the attack, and that it had not specifically targeted the National Health Service.<br/><br/>Similar incidents were reported from the United States, China, Russia, Portugal, Italy and many other countries.<br/><br/>Two security firms Kaspersky Lab and Avast said, they had identified the malware behind the attack in over 70 countries, although both said the attack has hit Russia the hardest.<br/>The Russian Interior Ministry confirmed it was hit by what it called ransomware attack. Microsoft said, it is pushing out automatic Windows updates to defend clients from the malware.<br/>