Hi,
I would be glad to answer your query.
There is not any workaround available to update definitions because Symantec is not releasing SEP 11 definitions anymore.
The initial end of support life date was originally scheduled for January 5th, 2014. All customers were provided a complimentary extention. No further extentions will be provided.
It's strongly recommended to upgrade to SEP 12.1, RU5 at the earliest to remain protected.