This is how malware beats Windows too
On Windows Vista and later versions, any change that affects all users requires the UAC prompt, unless it exploits a security weakness. Most malware does not exploit weaknesses. Instead, what malware now does is to install in a folder specific to the user. In Windows Vista, this is usually the %localappdata% folder (c:\users\<my name>\appdata\local\). If it installs there, there is no UAC prompt, but the appdata folder is also hidden so most people don't know to search there. So now the malware creators have discovered that the same trick to avoid prompting for a password in Windows now works on Macs. If the file installs in a location specific to the user and not the system, it beats the password.
