A method that you can use to enhance scanning performance is by limiting the files that Symantec Protection Engine scans.
You can limit the files that are scanned as follows:
Exclude specific file extensions and file types from scanning
When you enable this option, Symantec Protection Engine scans only the file extensions or the file types that are not in the exclude lists. The default file exclude lists contain the most common file extensions and the types that are unlikely to contain threats.
Block the files or email messages that meet or exceed a specific size from scanning
This option lets you specify the maximum size of files or messages to scan.
This option is available for the ICAP and Native protocols only.
From version 7.0, Native protocol has been deprecated. Symantec recommends the use of either ICAP or RPC protocol.