  This chapter introduces the concept of Autonomous Intelligent Cyber-defense
Agents (AICAs), and briefly explains the importance of this field and the
motivation for its emergence. AICA is a software agent that resides on a
system, and is responsible for defending the system from cyber compromises and
enabling the response and recovery of the system, usually autonomously. The
autonomy of the agent is a necessity because of the growing scarcity of human
cyber-experts who could defend systems, either remotely or onsite, and because
sophisticated malware could degrade or spoof the communications of a system
that uses a remote monitoring center. An AICA Reference Architecture has been
proposed and defines five main functions: (1) sensing and world state
identification, (2) planning and action selection, (3) collaboration and
negotiation, (4) action execution and (5) learning and knowledge improvement.
The chapter reviews the details of AICA's environment, functions and
operations. As AICA is intended to make changes within its environment, there
is a risk that an agent's action could harm a friendly computer. This risk must
be balanced against the losses that could occur if the agent does not act. The
chapter discusses means by which this risk can be managed and how AICA's design
features could help build trust among its users.
