  A hackfest named SWaT Security Showdown (S3) has been organized consecutively
for two years. S3 has enabled researchers and practitioners to assess the
effectiveness of methods and products aimed at detecting cyber attacks launched
in real-time on an operational water treatment plant, namely, Secure Water
Treatment (SWaT). In S3 independent attack teams design and launch attacks on
SWaT while defence teams protect the plant passively and raise alarms upon
attack detection. Attack teams are scored according to how successful they are
in performing attacks based on specific intents while the defense teams are
scored based on the effectiveness of their methods to detect the attacks. This
paper focuses on the first two instances of S3 and summarizes the benefits of
hackfest and the performance of an attack detection mechanism, named Water
Defense, that was exposed to attackers during S3.
