Which of the following is an essential characteristic of an effective information security system?

While unannounced inspections by senior management can contribute to accountability and oversight, they are not a fundamental characteristic of an effective information security system. Such inspections may provide short-term compliance checks but do not inherently ensure the ongoing effectiveness or adaptability of security measures.

Having multi-level management approval for policies is important for governance and support, but it does not directly affect the operational effectiveness of an information security system. Approval processes may help in establishing policies, yet they do not guarantee that the policies are implemented, monitored, or adjusted effectively over time.

Securing computers to workstations is a practical measure that adds a layer of physical security; however, it addresses only one aspect of information security. This characteristic does not encompass the comprehensive and dynamic nature of an effective information security system, which requires ongoing performance reviews and adjustments to adapt to new threats.