Hello,
I would suggest you to Install Liveupdate Administrator, which could install updates to all your Unmanaged clients.
Yes..yes..you can update virus definition on your Unmanaged Clients using Liveupdate Administrator.
Liveupdate Administrator version 2.3.2 is the Latest version available and is freely available from Symantec Technical Support Team.
Check this Article:
Is it Supported to Configure Unmanaged Symantec Endpoint Protection Clients to Update from LiveUpdate Administrator 2.x rather than the Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH123388
HOW TO change the LiveUpdate source of an unmanaged Windows Symantec Endpoint Protection 12.1 Client
http://www.symantec.com/docs/TECH166129
How to distribute definition content from a LiveUpdate Administrator 2.x (LUA 2.x) server to an isolated network.
http://www.symantec.com/docs/HOWTO44060
You could either Download the Liveupdate Administrator 2.3 from the Symantec FileConnect Website.
https://fileconnect.symantec.com/
OR
By Creating a case online with the Symantec Technical Support Team -
How to create a new case in MySymantec (formerly MySupport)
http://www.symantec.com/docs/TECH58873
OR
By Contacting the Symantec Technical Support Team -
Regional Support Telephone Numbers:
- United States: https://support.broadcom.com (407-357-7600 from outside the United States)
- Australia: 1300 365510 (+61 2 8220 7111 from outside Australia)
- United Kingdom: +44 (0) 870 606 6000
Additional contact numbers: http://www.symantec.com/business/support/contact_techsupp_static.jsp
Also, check this Article:
https://www-secure.symantec.com/connect/blogs/liveupdate-administrator-lua-version-232-now-available
Hope that helps!!