  The 1st International Workshop on Adaptive Cyber Defense was held as part of
the 2021 International Joint Conference on Artificial Intelligence. This
workshop was organized to share research that explores unique applications of
Artificial Intelligence (AI) and Machine Learning (ML) as foundational
capabilities for the pursuit of adaptive cyber defense. The cyber domain cannot
currently be reliably and effectively defended without extensive reliance on
human experts. Skilled cyber defenders are in short supply and often cannot
respond fast enough to cyber threats.
  Building on recent advances in AI and ML the Cyber defense research community
has been motivated to develop new dynamic and sustainable defenses through the
adoption of AI and ML techniques to both cyber and non-cyber settings. Bridging
critical gaps between AI and Cyber researchers and practitioners can accelerate
efforts to create semi-autonomous cyber defenses that can learn to recognize
and respond to cyber attacks or discover and mitigate weaknesses in cooperation
with other cyber operation systems and human experts. Furthermore, these
defenses are expected to be adaptive and able to evolve over time to thwart
changes in attacker behavior, changes in the system health and readiness, and
natural shifts in user behavior over time.
  The Workshop (held on August 19th and 20th 2021 in Montreal-themed virtual
reality) was comprised of technical presentations and a panel discussion
focused on open problems and potential research solutions. Workshop submissions
were peer reviewed by a panel of domain experts with a proceedings consisting
of 10 technical articles exploring challenging problems of critical importance
to national and global security. Participation in this workshop offered new
opportunities to stimulate research and innovation in the emerging domain of
adaptive and autonomous cyber defense.
