Row hammer is mitigated by issuing, to a memory device, mitigation operation (MOP) commands in order to cause the refresh of rows at a specified vicinity of a suspected aggressor row. These mitigation operation commands are each associated with respective row addresses that indicate the suspected aggressor row and an indicator of which neighbor row in the vicinity of the suspected aggressor row is to be refreshed. The mitigation operation commands are issued in response to a fixed number of activate commands. The suspected aggressor row is selected by randomly choosing, with equal probability, one of the N previous activate commands to supply its associated row address as the suspected aggressor row address. The neighbor row may be selected randomly with a probability that diminishes inversely with the distance between the suspected aggressor row and the neighbor row.