In May 2017 hundreds of thousands of computers across the world were hit by a massive ransomware attack called Wannacry. The perpetrators encrypted the contents of users' computers and demanded payment to unscramble their data. What made the threat worse was that it had the ability to literally spread virally across the Internet by exploiting connections between computers on networks. But where did it come from, what can we do to mitigate the threat, and who is at risk of attacks like this? Chris Smith, Kate Feller and Andrew Holding put these questions to cybersecurity expert Paul Harris, from the Manchester-based online security and ethical hacking company Secarma...