University College London , one of the world 's leading universities , has been hit by a major cyber-attack . The university describes it as a "ransomware" attack Attack.Ransom , such as last month 's cyber-attack which threatened NHS computer systems . The attack was continuing on Thursday , with access to online networks being restricted . The university has warned staff and students of the risk of data loss and `` very substantial disruption '' . University College London ( UCL ) is a `` centre of excellence in cyber-security research '' , a status awarded by the GCHQ intelligence and monitoring service . The central London university , ranked last week in the world 's top 10 , says that a `` widespread ransomware attack Attack.Ransom `` began on Wednesday . It was first blamed on so-called `` phishing '' emails , with links to destructive software . But later the university suggested it was more likely to be from contact with a `` compromised '' website , where clicking on a pop-up page might have spread a malware infection . Ransomware attacks Attack.Ransom are where computer systems are locked and threatened with damaging software unless payments Attack.Ransom are made . Students and staff were warned that `` ransomware damages files on your computer and on shared drives where you save files '' and were told not to open any suspicious attachments . The university says that it believes the risk of further infection has been contained , but it is urging staff and students to help with efforts to reduce any `` further spread of this malware '' . Universities , which often carry out commercially sensitive research , have become frequent targets for cyber-attacks . `` However , what makes this attack interesting is the timing , '' said Graham Rymer , an ethical hacker and research associate at the University of Cambridge . `` Hackers tend to target people who will be desperate to get access Attack.Databreach to their data and are , therefore , more likely to pay the ransom Attack.Ransom . `` Currently there are a lot of students who will be putting the final touches to their dissertations , so it could be that they were the targets . '' Mr Rymer said UCL seemed to have responded well to the attack and had `` locked it down pretty well '' . `` One thing UCL did is to quickly switch all drives in the system to `` read-only '' following the attack , which essentially prevented the malware from doing real damage . '' Mr Rymer said UCL may not have been the only intended target as he had seen other businesses facing the same malware . Last month , the National Health Service in England and Scotland was subject to a significant ransomware cyber-attack Attack.Ransom , as part of a global wave of attacks .