ESET's update files are usually not directly downloadable via a simple URL because they are designed to be accessed through the ESET software. However, you can manually update your ESET NOD32 by downloading the latest update files from ESET's servers.
For newer versions (v5 and above):
Open a working internet browser on a connected PC. Go to the official ESET download page: eset nod32 update file download direct
Business users with ESET Remote Administrator can set up a local update mirror. The tool EraMirror.exe can synchronize to a network share. ESET's update files are usually not directly downloadable