find the attach link
https://www-secure.symantec.com/connect/downloads/sep-policy-block-usb-and-exclude-keyboard-and-mouse
some other links
http://www.symantec.com/business/support/index?page=content&id=TECH105770&actp=search&viewlocale=en_US&searchid=1334609914324
http://www.symantec.com/business/support/index?page=content&id=TECH106304
http://www.symantec.com/business/support/index?page=content&id=TECH175220
http://www.symantec.com/avcenter/security/ADC/Configuring_Application_Control_1.1.pdf
Check these Threads:
https://www-secure.symantec.com/connect/forums/how-block-usb-using-sepm-windows-7
https://www-secure.symantec.com/connect/forums/usb-device-control-2
https://www-secure.symantec.com/connect/forums/sepm-121-application-and-device-control