Hello,
At the beginning, SecureAPlus will send hashes (a kind of thumbprint of the files) to server for scanning.
If the server doesn't have the hash recorded in its database, this means that it has never seen the file before. To scan a file, the server need to have the sample file. The server will find out which user has the file, and upload the file from the client machine. Universal AV only uploads executable files (such as .exe, .dll, .ocx, .com, etc.).
Regards,
Hendy