Hello,
Do you want to block an application because it is malicious in nature?
Check these Articles on how to configure SEP to block software.
Block Software By Fingerprint
https://www-secure.symantec.com/connect/articles/block-software-fingerprint
How to use Symantec Endpoint Protection to block or log legitimate but unauthorized software usage
http://www.symantec.com/docs/TECH97618
Configuring system lockdown
http://www.symantec.com/docs/HOWTO80848
In case, you want Symantec to block those malicious application, you can also submit these suspicious files to the Symantec Security Response Team on :
https://submit.symantec.com/websubmit/essential.cgi
We also offer a self-service site to analyze files, at http://www.threatexpert.com, which can give you more information on the files you submit to it.
What to do when you suspect that a Symantec AntiVirus product is not detecting viruses
http://www.symantec.com/docs/TECH99222
Check this Article:
Using Symantec Help (SymHelp) Tool, how do we Collect the Suspicious Files and Submit the same to Symantec Security Response Team.
Hope that helps!!