VIRUSES are mainly executable files (.exe files)

Most of the VIRUS has ICON of a Normal folder so USER's get confused.

Thinking it as FOLDER user double clicks on it.

As soon as file is opened VIRUS program in the executable file gets executed and infects the whole Operating System.

Mostly the VIRUSes are transferred through one system to other via USB sticks (Pendrive)

So to protect your system from USB virus, never open the USB by the autoplay option displayed on connecting the USB

And Never Open your USB by double clicking the icon displayed in myComputer.

Always open your pen drive by right click and EXPLORE option. This will avoid virus to affect your system.