What is a denial-of-service (DoS) attack?

A denial-of-service (DoS) attack is defined as a malicious attempt to disrupt the normal functioning of a service or network by overwhelming it with excessive traffic. This can be achieved through various means, such as flooding the target with numerous connection requests, which can exhaust resources and render the service unavailable to legitimate users. The core intent of a DoS attack is to deny access to resources, hence the name, and to create a significant impact on service availability, thereby affecting business operations and user experience.

The other options relate to different cybersecurity concepts. Unauthorized access to confidential information pertains to breaches of security that target data protection, rather than service availability. Methods of encrypting data focus on securing data from unauthorized access, which is unrelated to service disruption. Lastly, defense against external cyber threats encompasses a broad range of protective measures but does not specifically address the mechanics or purpose of a DoS attack. Understanding the nature of a DoS attack is crucial for implementing effective defensive strategies and ensuring the resilience of services and networks against such threats.