Look at it this way: you are asking how to disable a mechanism that is designed to protect you from yourself. After you click on an Install instruction, the OS should automatically enter the admin name associated with your account into the authentication window, leaving you to enter only the relevant password. Given the stakes (ie what is at risk), this is hardly an onerous chore. The admin name and password are then scrutinized by the combination of Netinfo and Kerberos. They authorize the task if the name and password pass the examination by those software guards. No software can be installed by stealth, and if you do not make a conscious choice to install every software package that you do install, you will give real meaning to your screen name.
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