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Microsoft

Microsoft is the maker of Windows, the operating system on most home computers, and of the Defender malware protection built into it.

Microsoft is the maker of Windows, the operating system that runs most home computers in the UK, and of Microsoft Defender, the malware protection tool built into Windows1. This site mentions Microsoft not as emergency kit but because of what its software means when things go wrong: a household that keeps Windows updated and its files backed up is far better placed to get through a cyber incident, and a computer that has missed its updates is the one that gets hit.

Keep Windows updated, automatically

The National Cyber Security Centre (NCSC) advises applying updates to your apps and device software as soon as they are available, because updates include protection from viruses and other malware2. The simplest way is to turn on automatic updates in your device's settings, so you do not have to remember2. Hackers rely on people ignoring update notifications so they can get in before the update is made3. Make sure your antivirus, including the built-in Microsoft Defender, is turned on, up to date and set to receive updates automatically1.

What WannaCry showed about missed updates

On Friday 12 May 2017 a ransomware attack known as WannaCry was released worldwide4. WannaCry encrypted data on infected computers and demanded a ransom payment to allow users access again4. It only affected computers running Microsoft Windows operating systems that did not have the latest security patches installed5. Infected organisations all shared the same vulnerability: unpatched, or unsupported, Windows operating systems4.

Microsoft had issued a patch to address the underlying vulnerability on 14 March 2017, two months before the attack6. NHS Digital had issued critical alerts in March and April 2017 warning organisations to patch their systems, and had this advice been acted on in a timely manner, the scale and impact of the attack could have been much reduced6. The lesson for any household is plain: when an update arrives, install it.

Older versions of Windows

The NCSC strongly recommends that you do not continue to use unsupported operating systems, but instead upgrade to one which receives regular security updates from the vendor5. Older devices eventually stop receiving updates altogether2.

Even so, Microsoft did protect its oldest systems when WannaCry struck. Computers running Windows 7 could have protected themselves by applying a patch Microsoft issued in March 20174, and users of Windows 7, 8, 8.1 or Windows 10 with automatic updates turned on were already protected automatically5. Immediately after the attack, Microsoft issued a patch for Windows XP that would prevent WannaCry and similar ransomware4, and the NCSC advised Windows XP, Vista and older versions to download and install that security update5.

Fake Microsoft warnings and phone numbers

Scammers use official-sounding messages about resetting passwords, receiving compensation, scanning devices or missed deliveries, often full of technical language and urging you to act immediately8. A warning message on your screen asking you to call a phone number is not from Microsoft. Do not call it. If you have received nuisance, suspicious or unwanted calls, hang up and contact your phone provider8. Forward suspicious text messages to 7726, a free service for reporting spam9.

Back up what matters

A backup is a copy of your important data stored in a separate safe location, usually cloud storage or removable media such as a USB stick, SD card or external hard drive10. Back up photos and key documents, and consider cloud services, many of which offer an amount of storage for free5. If a device is infected, restore your data from the last known good backup; you will lose anything not backed up, but trying to rescue data while the device is still infected risks carrying the infection through after wiping and reinstalling7. If any of your accounts use the same password as one affected in a breach, change them as well9.

For the wider picture of cyber incidents and what a household should do, see our guide to cyber attacks and major IT failures, and for keeping devices running through a power cut, see backup power at home and staying informed in an emergency.

Sources (10)
  1. WannaCry guidance for home users and small businesses, National Cyber Security Centre, 2017-05-16
  2. Install the latest software and app updates, National Cyber Security Centre, 2021-12-21
  3. Cyber security, Essex Prepared, 2026-10-29
  4. Investigation: WannaCry cyber attack and the NHS, National Audit Office, 2017-10-27
  5. Ransomware WannaCry guidance for home users and small businesses, National Cyber Security Centre, 2017-05-16
  6. Lessons learned review of the WannaCry ransomware cyber attack, NHS England, 2018-02-01
  7. Sole infected devices, National Cyber Security Centre, 2026
  8. Data breaches, National Cyber Security Centre, 2021-01-28
  9. Data breaches infographic, National Cyber Security Centre, 2023
  10. Always back up your most important data, National Cyber Security Centre, 2021-12-21

Common questions

Does Windows have a free tool for moving my files to a new computer?

The National Cyber Security Centre advises keeping a backup of your important data in a separate safe location, either in cloud storage or on removable media such as an external hard drive, USB stick or SD card. If you already follow that advice, moving to a new computer is straightforward: you restore your files from the backup. Most cloud providers can back up automatically, daily or weekly, so the copy is ready before you need it.

A warning message on my screen shows a Microsoft phone number. Should I call it?

No. Scam messages often use official-sounding language about resetting passwords, scanning devices or missed deliveries, and urge you to act immediately. Microsoft does not work this way. Hang up or close the message, do not call the number, and if you have received nuisance or suspicious calls, contact your phone provider. Suspicious text messages can be forwarded free to 7726.

What happens when Windows stops getting updates on an old computer?

The National Cyber Security Centre says an unsupported device will not receive updates, including security fixes, and it strongly recommends upgrading to a system that still receives regular security updates from the maker. Older devices eventually stop receiving updates altogether, so an old machine should not be relied on for anything important during an emergency.

What happens if I miss a month of Windows updates?

Turn on automatic updates in your device's settings so you do not have to remember. Hackers rely on people ignoring update notifications so they can get in before the update is made. Updates include protection from viruses and other malware, and the National Cyber Security Centre advises applying them as soon as they are available.

Was Windows 7 protected against WannaCry?

Yes, if updates were applied. Computers running Windows 7 could have been protected by a patch Microsoft issued in March 2017, before the attack on 12 May 2017. The National Cyber Security Centre confirmed that Windows 7, 8, 8.1 and 10 with automatic updates turned on were already protected.

Did Windows XP get a patch for WannaCry?

Yes. Immediately after the WannaCry attack in May 2017, Microsoft issued a patch for Windows XP that would prevent WannaCry and similar ransomware, even though XP was no longer supported. The National Cyber Security Centre still strongly recommends not continuing to use unsupported operating systems.