1. Apparatus for passively tracking expired data in a dynamic memory, the apparatus comprising: an error encoding circuit, the error encoding circuit being operative to receive an input data word and to generate an encoded data word which is stored in the dynamic memory; a first decoding circuit, the first decoding circuit being operative to receive an encoded data word from the dynamic memory, to detect at least one or more unidirectional errors in the input data word read from the dynamic memory, and to generate a first error signal when at least one error is detected, the first error signal indicating that the input data word read from the dynamic memory comprises expired data; and control circuitry configured for initiating one or more actions in response to the first error signal.