It is our pleasure to welcome you to the 12th ACM Workshop on Artificial Intelligence and Security - AISec 2019. AISec, having been annually co-located with CCS for 12 consecutive years, is the premier meeting place for researchers interested in the intersection of security, privacy, AI, and machine learning. Its role as a venue has been to merge practical security problems with advances in AI and machine learning. In doing so, researchers also have been developing theory and analytics unique to this domain and have explored diverse topics such as learning in game-theoretic adversarial environments, privacy-preserving learning, and applications to malware, spam and intrusion detection. AISec 2019 received 40 submissions, of which 10 (25%) were selected for publication and presentation as full papers. Submissions arrived from researchers in many different countries, from a wide variety of institutions both academic and corporate. |