A method, system or computer usable program product for masking communication data using context based rules including intercepting a communication between a server and a client by an intermediary, the communication having a recipient, parsing the communication by the intermediary to determine whether a context based alteration rule should be applied, responsive to an affirmative determination, applying the rule to the communication to produce an altered communication with altered data, and sending the altered communication to the recipient so that the altered data in the communication is utilized in a masked manner.