Hi,
In SEP 11.x you can block autorun.inf through multiple way with the help of following articles.
Preventing a virus from using the AutoRun feature to spread itself
http://www.symantec.com/docs/TECH104447
Preventing viruses using "autorun.inf" from spreading with "Application and Device Control" policies in Symantec Endpoint Protection (SEP) 11.x
http://www.symantec.com/docs/TECH104909
Microsoft KB articles to disable Autorun
http://support.microsoft.com/kb/967715
http://technet.microsoft.com/en-us/magazine/cc137730.aspx
From SEP 12.1 onwards, SEPM will block autorun.inf by default. It's a part of Application & device control policy.
I hope it will help you !!!