  Digital manufacturing (DM) cyber-physical system is vulnerable to both cyber
and physical attacks. HACK3D is a series of crowdsourcing red-team-blue-team
events hosted by the NYU Center for Cybersecurity to assess the strength of the
security methods embedded in designs using DM. This study summarizes the
lessons learned from the past three offerings of HACK3D, including ingenious
ways in which skilled engineers can launch surprising attacks on DM designs not
anticipated before. A key outcome is a taxonomy-guided creation of DM security
benchmarks for use by the DM community.
