  We introduce the new version of SimProp, a Monte Carlo code for simulating
the propagation of ultra-high energy cosmic rays in intergalactic space. This
version, SimProp v2r4, together with an overall improvement of the code
capabilities with a substantial reduction in the computation time, also
computes secondary cosmogenic particles such as electron-positron pairs and
gamma rays produced during the propagation of ultra-high energy cosmic rays. As
recently pointed out by several authors, the flux of this secondary radiation
and its products, within reach of the current observatories, provides useful
information about models of ultra-high energy cosmic ray sources which would be
hard to discriminate otherwise.
