Which of the following are potential consequences of a lack of availability?

A lack of availability primarily leads to a loss of functionality. Availability is one of the key pillars of the information security triad, which also includes confidentiality and integrity. When systems or data are not available, users are unable to access essential services, applications, or information when needed. This disruption can severely impact operations, potentially halting business processes and affecting overall productivity.

While data breaches and increased costs can stem from various issues in an organization's cybersecurity posture, they are not directly a consequence of availability problems. Improved efficiency would generally be the opposite effect one would expect when availability is compromised, as decreased access typically leads to slower operations rather than enhancements in efficiency. Hence, the most accurate reflection of the consequences of a lack of availability is the loss of functionality.