1. A method for operation upon one or more data processors to assign a reputation to a messaging entity, the method comprising: receiving a communication from a messaging entity; deriving a risk profile for the communication comprising: queuing the communication for interrogation by a plurality of interrogation engines, each interrogation engine of a particular type designed to test the communication for a particular security risk; performing a load evaluation on an interrogation engine of one of the particular types based upon the plurality of interrogation engines queued to interrogate the communication; determining that the load evaluation exceeds a threshold, and in response adjusting the plurality of the interrogation engines by generating a new instance of an interrogation engine of the one of the particular types based upon the plurality of interrogation engines queued to interrogate the communication; aggregating output of the plurality of interrogation engines with data associated with previously received communications to form the risk profile for the communication; determining, using one or more data processors, a reputation score associated with the communication based upon the risk profile; wherein the reputation score is indicative of reputation of the messaging entity; wherein the determined reputation score is used in deciding what action is to be taken with respect to communications associated with the messaging entity.