1. A system for assessing security risk, the system comprising at least one processor programmed to: maintain a plurality of records, wherein: each record is associated with a respective network address in a plurality of network addresses; and each record comprises information regarding user behaviors observed from a plurality of previous electronic transactions that have been tagged with the network address associated with the record; receive log information regarding a present electronic transaction; use the log information to determine at least one network address from which the present electronic transaction is requested; and analyze the log information regarding the present electronic transaction in combination with history information associated with the at least one network address, wherein the history information is based on the record associated with the at least one network address and is indicative of at least one user behavior observed from the plurality of previous electronic transactions that have been tagged with the at least one network address; and while the present electronic transaction is still on-going, provide an updated risk assessment for the at least one network address based on a result of analyzing the log information regarding the present electronic transaction in combination with the history information associated with the at least one network address.