With or without another device (such as CSC module, Websense,Cisco Cloud Web Security , Ironport or locally?
If locally would be using regex:
Here u go:
https://supportforums.cisco.com/docs/DOC-1268
Regards,
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC