As new threats emerge, Symantec immediately builds new protection updates and makes them available for download on a subscription basis.

Note: The i32 Intelligent Updater package cannot be used to update Symantec AntiVirus Corporate Edition 8.0, 9.0, or 10.0 servers or Norton AntiVirus Corporate Edition 7.6 servers, but can be used to update Corporate Edition clients. The x86 Intelligent Updater package can be used to update Corporate Edition clients and servers.

You can get the latest virus definitions from here.