Malware

Malware is software written to cause harm once it is running on a device. It is installed in order to steal data, damage or delete it, lock it so the owner cannot open it, or hand control of the device to someone else. Malware is the umbrella name for the whole family of harmful programs.

How it gets onto a system

Most malware does not break in on its own: a person has to let it in, and that usually means running something. The file often looks perfectly ordinary — a homework document, a page of class notes, an add-on for a game — but hidden instructions are tucked inside it, and they start running the moment it opens. Installing a program can bring malware with it too, quietly adding extra software nobody asked for. A removable storage device that already carries malware can pass it on as soon as it is plugged in.

For example, you install a free drawing app called Star Sketcher that a friend sent you the link for. It draws perfectly well, but a hidden part of it lets a stranger in: they can switch on your webcam and read through your files whenever they choose. Nothing on the laptop has broken — it still switches on and runs every program exactly as before — but someone else is now in charge of it.

The threat it poses

Once it is running, malware does whatever it was written to do. It might send copies of your files to the attacker, hold them hostage until you pay, wipe them altogether, or simply hand control of the machine over so that the device follows their instructions rather than yours. Notice where the harm lands: on the data, or on who is in control of the device — not on the hardware itself.