Which of the following describes a Denial of Service (DoS) attack?

A Denial of Service (DoS) attack is characterized by an attempt to make a system, service, or network unavailable to its intended users. This is typically achieved by overwhelming the target with a flood of illegitimate requests or data from a single source, thereby exhausting its resources and rendering it incapable of responding to legitimate users.

In this context, the correct choice accurately reflects that a DoS attack originates from a single source, focusing on obstructing access to the system. This type of attack aims to disrupt normal operations and prevent users from accessing the services they expect.

The other choices do not correctly describe a Denial of Service attack. For instance, distributing malware from multiple computers refers to a different type of attack, often associated with Distributed Denial of Service (DDoS) attacks, where multiple systems overwhelm a target. Breaches of data integrity typically involve unauthorized alterations to data rather than the availability of a service. Lastly, a technique to recover stolen data does not relate to DoS attacks; rather, it pertains to data recovery practices. Thus, the selected answer appropriately captures the essence of a DoS attack and distinguishes it from other types of cybersecurity threats.