Open the Isa Management console, expand your server or array, right click on IP packet filters and select new.
Call it Symantec Liveupdate (1)
Click next, you will see the screen below.
Click on Filter type.
Enter the details as in screen below.
Click on local computer
Use whichever IP address corresponds to your external (Non LAT ip address), in this case default.
Click on Remote Computer and enter the Symantec LiveUpdate Server IP address
Repeat above procedure for the remaining IP Addresses and your should have the following packet filters in ISA.