Network attack defense includes: obtaining a set of one or more statistical attributes for a protected site by gathering statistics for a set of one or more site attributes of the protected site, the site attributes indicating an operation mode of the protected site; determining, based on the set of one or more statistical attributes, that the protected site is to transition from a current operation mode to a target operation mode, wherein the current operation mode has a current defense strategy different from a target defense strategy of the target operation mode; and if the protected site is to transition from the current operation mode to the target operation mode, transitioning from the current operation mode to the target operation mode and applying the target defense strategy for the protected site instead of the current operation mode.