Which of the following is considered a major cyber threat?

Unauthorized data access is indeed a major cyber threat because it involves individuals or entities gaining access to sensitive, confidential, or proprietary information without permission. This can lead to data breaches that compromise personal information, intellectual property, or organizational secrets, with significant consequences for both individuals and organizations. Cybercriminals often target networks and databases to extract valuable information, which can be used for identity theft, fraud, or corporate espionage.

In the context of cybersecurity, protecting against unauthorized data access is crucial for maintaining privacy, ensuring regulatory compliance, and safeguarding a company's reputation. Effective measures include implementing strong authentication protocols, conducting regular security audits, and educating employees about social engineering attacks, all of which help mitigate these theft risks.

Other options, while potentially harmful, do not fall within the primary definition of cyber threats. Physical theft of hardware is a security risk but does not directly relate to cyber threats in the same way that unauthorized data access does. Customer complaints can indicate customer service issues but do not pose a direct threat to the cyber environment. Operational downtime may result from various issues, including cyber attacks, but it is more an effect of interruptions rather than a direct threat itself. Therefore, unauthorized data access stands out as a primary concern in the landscape of cybersecurity threats.