What is a significant characteristic of a Denial of Service (DoS) attack?

A significant characteristic of a Denial of Service (DoS) attack is that it aims to exhaust the resources of a targeted service. This type of attack overwhelms a system, service, or network with a flood of traffic or requests, causing it to become slow, unresponsive, or completely unavailable to legitimate users. By consuming the available bandwidth, processing power, or memory of the target, the DoS attack effectively disrupts normal operations, thereby denying access to users who need to interact with the targeted service.

In contrast, some other options describe different types of attacks or malicious activities that do not fall under the category of DoS. For instance, encrypting files to hold them hostage is characteristic of ransomware attacks, which focus on monetary gain by extorting users. Targeting physical assets is more related to physical security threats, rather than cyber threats like DoS. Lastly, collecting sensitive data from users pertains to data breaches or interception attacks, which seek to compromise confidentiality rather than availability.