Dirty is a  Winboard compatible chess engine. It is an hybrid between BUZZ (Pradu Kannan and Fonzy Bluemers, search) and EveAnn (Andres Valverde, evaluation). At 6 Nov, 2008 it looks a bit stronger than its parentals

For more info go to the Dirty Chess Engine Site

If you only are looking for old versions, here are some :
Dirty logo
logo by Jim Ablett