You are using JAMF Composer now right?
If so you "may" be able to get wat you want by installiby making aackage or packages holding definitions. Just fire up Composer, have Symatec download the definitions and then ask Compser to make a package with all the files Symatec changed. Note however that the nature of virus defs is to become quickly outdated.
Same procedure for Java.
But it sounds like what you may really want is to disable Apple Software Update? If so you can set up the service on your server, tell it not to install any updates unless you approve them. Then don't approve any. This will effectively disable Apple Software Update.