Homemade t-shirts are starting to be more commonplace at Defcon, now that several vendors offer a "make your own custom silkscreened t-shirt on the premises" service. However, this guy (and his compadre, not shown) had these shirts made before the show. Both work for a company that provides security for SCADA (Supervisory Control And Data Acquisition) systems, such as the kind that are used to operate power plants.

Homemade t-shirts are starting to be more commonplace at Defcon, now that several vendors offer a "make your own custom silkscreened t-shirt on the premises" service. However, this guy (and his compadre, not shown) had these shirts made before the show. Both work for a company that provides security for SCADA (Supervisory Control And Data Acquisition) systems, such as the kind that are used to operate power plants.