Which activity is involved in denial of service attacks?

Denial of service attacks specifically involve overloading a service to the point where it becomes disabled or unavailable to legitimate users. This type of cyberattack aims to disrupt the normal functioning of a server, service, or network by overwhelming it with a flood of traffic, causing it to slow down significantly or crash entirely. The intention behind this is to deny service to legitimate users, making it detrimental to business operations and user access.

The other activities listed do not correlate with the primary objective of denial of service attacks. Unauthorized access to devices refers to hacking or gaining illegal access, which does not focus on service disruption. Aiding in data recovery efforts and enhancing online security measures are proactive measures designed to protect against attacks and recover from them, rather than being directly involved in the act of causing service denial. Therefore, the focus on service overload is what makes the correct answer clear in the context of denial of service attacks.