Malwares attack computers by modifying the system files and registry so that it will be executed automatically every time the computer turn on. UAC will ask our permission before letting the malwares attack our computers. Malwares will never have the chance to attack our computer if we do not disable UAC and click "No / Cancel" button when the UAC ask our permission. Don't simply click "Yes / Continue" button if we don't really know what the program is!
Thus, don't ever disable UAC or you will become one of the victim attacked by malwares!
Don't ever click "Yes / Continue" button (in UAC prompt) if you don't really know what the program is!
Click "No / Cancel" button (in UAC prompt) if you don't know the program is malware or not.
The best policy is:
Set the UAC settings to the highest level: