After a cyber-attack disrupted IT works across the globe, many people have written to the BBC with questions about why it happened, how you can protect your computers and smartphones, and if the attackers will be caught.
BBC Technology reporter Chris Foxx and security expert Prof Alan Woodward provide some answers.
Why doesn’t the NHS worked a closed procure system, like the military forces?
“Practically speaking, it’s not possible to altogether isolate the NHS network, ” read cyber-security professional Prof Alan Woodward.
“The NHS moves emails to patients who have email addresses outside of the NHS network.