Secordit home
Contact

What is malware?

Malware, short for malicious software, is harmful software on a phone, tablet or computer. These programs are made to harm a device or the information on it, or to use it without the owner's permission. The harm can include stealing information, locking files, or deleting them. Ransomware is one type. 1

By Secordit. Last checked: 10 November 2026.

Go to the steps · All glossary terms

How it works

  1. A risky email attachment, a file on a USB stick, or a harmful website can put malware on a device. 12
  2. The program may steal information, lock or encrypt files, or delete them. Not every unusual email is malware. 1
  3. A later scam call may claim the device is infected and offer to fix it. That call is a trick. 3

How it can look

The NCSC warns that unsolicited calls claiming your device is infected, and offering to fix it, are a common scam. Hang up, then use the NCSC recovery guidance and report the call to Report Fraud. 36

Warning signs

  • A security tool reports malware, or files become locked or unusable. 12
  • An unsolicited caller says your device is infected and offers to fix it. 3
  • An unexpected message asks you to open an attachment, run a file, or install software. 12

What to do now

  1. If you can, confirm the problem with a security alert or a scan on a PC or laptop. 23
  2. Follow the NCSC steps for an infected device. On a phone or tablet this may involve a factory reset, which can lose unsaved data. 3
  3. Hang up on unsolicited calls that claim your device is infected and offer to fix it. Report those calls to Report Fraud. 36

UK reporting and support

  • If money has gone or banking details were shared, call your bank using the number on your card. Or use 159 if your bank participates. 7
  • For fraud or hacking in England, Wales or Northern Ireland, use Report Fraud. In Scotland, call Police Scotland on 101. 689
  • The NCSC also publishes help for an infected device and for a hacked account. 43
  • If someone is in danger, call 999. 89

How to protect yourself

  • Keep the built-in antivirus included with a Windows or Apple computer switched on and updated. The NCSC says switching it on makes you safer. A trial third-party product may not work alongside the built-in tool, and could stop it working. You may want to research your own choice. 1
  • Apply software updates, and do not ignore update prompts. 12
  • Be careful with unexpected attachments, files on a USB stick, and unfamiliar websites. 12

Frequently asked questions

How can I tell if my laptop has malware, and what should I do first?

Look at any alert from the security tool already on the computer, and run a scan if you can. Then follow the NCSC steps for an infected device, rather than advice from an unexpected caller. 23

Do I need to buy a separate antivirus product?

The NCSC says a built-in antivirus tool is often included with Windows and Apple computers, and that switching it on makes you safer. A trial third-party product may not work alongside that built-in tool, and could stop it working. You may want to research your own choice. 1

Is ransomware a type of malware?

Yes. Ransomware is malware that encrypts files and demands a payment. The NCSC's ransomware guidance says that if you do pay, that does not mean you will get access to your data or computer. 15

Matching kit

First Hour After a Breach · £29 · Digital download.

An incident-response planning kit for UK small businesses. It is not a live incident-response or legal service.

General information, not legal, financial or personalised security advice. Secordit is not a police or bank reporting service.

News Pulse

Account security, explained by email.

Read about News Pulse

Sources

  1. NCSC, What is an antivirus product? Do I need one? | National Cyber Security Centre. Accessed 10 November 2026 (Europe/London).
  2. NCSC, Infected devices | National Cyber Security Centre. Accessed 10 November 2026 (Europe/London).
  3. NCSC, How to recover an infected device | National Cyber Security Centre. Accessed 10 November 2026 (Europe/London).
  4. NCSC, Help for individuals | National Cyber Security Centre. Accessed 10 November 2026 (Europe/London).
  5. NCSC, What you need to know about ransomware | National Cyber Security Centre. Accessed 10 November 2026 (Europe/London).
  6. Report Fraud, Report Fraud. Accessed 10 November 2026 (Europe/London).
  7. Stop Scams UK, 159 Phone number - Stop Scams UK. Accessed 10 November 2026 (Europe/London).
  8. Police Scotland, How to report a crime - Police Scotland. Accessed 10 November 2026 (Europe/London).
  9. Report Fraud, Reporting cyber crime and fraud or phishing attempts - Report Fraud. Accessed 10 November 2026 (Europe/London).