A method, an apparatus, and a device for detecting an electronic mail (E-mail) attack. The device receives a data flow, obtains an E-mail traffic parameter of each statistic period within a predetermined number of statistic periods, where within each statistic period, the E-mail traffic parameter of each of the statistic periods is determined according to a protocol type of the received data flow, and determines that an E-mail attack is detected when the E-mail traffic parameter of each statistic period within the predetermined number of statistic periods matches a first threshold.