With more than 200,000 victims in 150 different countries, many are braced for more attacks to come.
But as workers across the globe head back into the office at the start of the working week, how will you know if your computer has been infected?
The National Cyber Security Centre (NCSC) has issued a statement on their website, offering advice to both organisations and private individuals on how to protect themselves from further attacks.
:: How can you tell if your computer has been infected?
The ransomware called Wanna Decrypt, also known as WannaCry, encrypts files on the machine, effectively locking them.
A message will appear onscreen with a ransom demand, countdown timer and Bitcoin wallet to pay the anonymous virtual payment into.
People have been asked to pay ransoms of $300 (£230) or more to regain access to their computers.
While 47 NHS health trusts across England have so far been affected, the good news is that home users are believed to be at low risk to this attack.
:: How can you protect your system?
The malicious software only infects machines running Windows operating systems, so Windows users should immediately run a Windows Update.
An up-to-date anti-virus programme should also be in place – this can stop ransomware from being downloaded.
A full scan should be carried out – this will locate any malware that may have already found its way onto your computer.
Important data should be backed up – you can’t be held to ransom if you’ve got the data somewhere else.
An external hard drive is particularly useful here, as it doesn’t need to be connected to the internet, and can keep your valuable information at a distance from the hackers.
Exercise caution when opening emails – and don’t click on any attachments or links sent to you by an unknown sender.
Never download an app that hasn’t been verified by an official store
A final fail-safe is to shut down vulnerable systems.
:: How does the virus spread?
There are a number of ways, including opening attachments or links in phishing emails or downloading legitimate-looking programmes that contain the malware.
Another method, which preys on machines using outdated software, is visiting a malicious site.
Once inside a network the virus – described as a “ransomware worm” – can then spread to other connected computers.
:: What do you do if your computer is infected?
The National Crime Agency encourages victims not to pay any ransom and to contact Action Fraud – the UK’s national fraud and cyber crime reporting centre
Some programmes are available to help decrypt files, but if you have backed up all your data you will be able to restore your device using that.
More information and support can be found on the NCSC website.