The term describes malicious purpose or behavior rather than one particular file format or technique. Different forms can affect the confidentiality, integrity or availability of information and systems. A program's claimed purpose does not establish what it actually does.
For example, an apparently useful application may secretly collect private information without authorization. Assessing a specific incident requires evidence of the software's behavior and access; a reported installation alone does not prove every claimed consequence.
ELI5
Malware is computer software designed to do something harmful or unauthorized. It can interfere with information or with the way a device works.
For example, a program may promise to help but secretly copy private files. The problem is what it does, even if its name or appearance seems trustworthy.
Is every software error malware?
No. An accidental defect can cause harm, while malware involves malicious or unauthorized purpose or behavior.
Does malware affect only stored files?
No. It can also interfere with applications, system operation or information being processed or communicated.
