Install Sophos on Mac OS 10.8
By default, Mac OS 10.8 only allows users to install applications from ‘verified sources’. BOL downloads are not verified; therefore, upon installation you will receive the error message: “Downloaded Program.mpkg” can’t be opened because it is from an unidentified developer.
To allow the installation:
Go to System Preferences—> Security & Privacy
Click on the lock icon in the bottom, left corner and enter the Admin password
In the General Tab, under the header “Allow applications downloaded from:”, choose Anywhere.