Hi Mohan,
Please read carefully below note
For blocking , first u need to identify false negative incident correctly otherwise ur bussiness will hamper. so that u need to first designe and implement matured policies. after this evalutate the incident detection till accuracy u achive for false negative incidents .After then u can proceed to block confidentail data for blocking with responce rules featurs that DLP has.
Also refer
Symantec Data Loss Prevention Network Monitor inspects all network communications,
such as email, instant messages (IM), Web, FTP, P2P, and generic TCP, for confidential
data in violation of data security policies.
Symantec Data Loss Prevention Network Protect automatically protects stored
confidential data by quarantining, copying, or removing it from its stored location.
Symantec Data Loss Prevention Network Prevent proactively stops network
communications from being sent in violation of data security policies by conditionally
removing or routing messages that contain confidential data to an encryption gateway
for secure delivery.
Symantec Data Loss Prevention Endpoint Prevent blocks confidential files from being
copied to USB or other removable media devices, transferred over the network, burned to
CD/DVDs, copied to a drive, or printed or faxed electronically.
Also find the sheet for more details
https://www-secure.symantec.com/connect/forums/symantec-dlp-network-prevent-mail-quarantine-and-block-response-rules
https://www-secure.symantec.com/connect/articles/chapter-2-concept-dlp-monitoring-and-blocking-confidential-data