Hello,
What you need:
1) Latest Certified Definitions from Symantec.
Please download the latest certified definitions from Symantec website at:
http://www.symantec.com/security_response/definitions/download/detail.jsp?gid=savce
Download the definitions for Symantec Endpoint Protection Manager 12.1 ( .jdb format). File may be saved as .zip, please rename the file to .jdb when the download is complete.
Check this Article:
How to manually update definitions for a managed Symantec Endpoint Protection Client using the .jdb file
http://www.symantec.com/docs/TECH104363
2) LiveUpdate Installer shipped with the release of Symantec Endpoint Protection in use.
The file is located in the SEPM folder on the installation media. The filename is lusetup.exe
Reference:
The Symantec Endpoint Protection Manager does not update virus definitions successfully through LiveUpdate
http://www.symantec.com/docs/TECH183178
Hope that helps!!