Hackers will sometimes encourage you to keep your computer on and linked to the network, but don't be fooled.
Dozens of state-run National Health Service (NHS) hospitals were hit, many closing their doors to emergency cases and cancelling routine appointments and surgery. Another employee said it was 'chaos'. If you are still unsure what to do, contact the hospital directly.
"Our IT teams have been working throughout the weekend to ensure that computers across the Trust are safe for staff to use".
NHS England said that, as of 3pm on Monday, two hospitals remained on divert following the attack, down from seven on Sunday.
Riverbank IT Management managing director Malcolm Newdick said: "Last week's ransomware attack was the most unsafe malware attack we have seen. Please see our guidance on emergency supply and our mythbuster on emergency supply which we hope supports you over this hard time". There is an emergency committee that is reporting constantly and we have conference calls every eight hours. "We've been saying for some time that maybe it would take some kind of major incident to move it up".
One person helping coordinate banks' response said they were setting up back-up systems for data and introducing security upgrades.
NHS Digital has announced updated guidelines on protecting against future cyber-attacks including instructions to install a patch to protect systems against further attacks and malicious viruses.
It follows the "ransomware" cyber-attack which left NHS trusts across the United Kingdom without access to IT facilities and patients records.
Microsoft said the situation was "painful" and that it was taking "all possible actions to protect our customers".
"But at the same time, I also know that if you're someone who's been affected and you've lost all your children's photographs or you've lost all your data or you lost your thesis, sometimes $300 is worth it, you know?"
"In the NHS, the technology they are using it out of date", said Paul Edon of cyber security group Tripwire.
At the hospital on Friday, patient Patrick Ward had been shaved and had his catheter fitted ready for a long-awaited heart operation when the attack happened.
NHS Digital confirmed that the patch was made available on its cyber portal on April 25, and a link sent to NHS IT staff on April 27.
MalwareTech, who works for cybersecurity firm Kryptos Logic, is part of a large global cybersecurity community who are constantly watching for attacks and working together to stop or prevent them, often sharing information via Twitter.
China is also set to implement a tougher new cyber security law from June 1, created to strengthen critical infrastructure, even as many global tech firms and lobbies say that its cyber rules skew the playing field against foreign firms.
Problems with cyber security in NHS organisations were highlighted past year by Dame Fiona Caldicott, the national data guardian, who warned that issues were given insufficient priority and that health bodies persisted in using obsolete computer systems, The Times said.