How it works
Malware describes software or firmware used for harmful or unauthorised actions. The category includes different behaviours: stealing information, encrypting files, displaying unwanted advertisements or using a device for another person’s work. A virus is one type, not a synonym for every infection.
A practical example
An apparently useful installer may also add an unwanted programme that changes browser behaviour. Another infection can operate quietly and take credentials without visible pop-ups. The absence of a dramatic warning therefore does not establish that a device is clean.
What to check
Record the symptoms, affected files and any security detection. Run supported, updated protection and stop entering sensitive credentials if compromise is suspected. On a work device, notify the responsible administrator. Keep important recovery information and verified backups separate before attempting a destructive reset or reinstall.
Limits and safe use
Slowness, crashes and high fan speed also have non-malware causes, including storage, cooling and legitimate background work. Avoid downloading a cleaner from a scare pop-up. A scan result should guide investigation, not replace it; restoring the computer and securing exposed accounts may both be necessary.