What is the purpose of a rootkit?

A rootkit is primarily designed to gain administrative control over a system while concealing its existence and the presence of other malicious software that may be running. This control allows an attacker to manipulate the system undetected, execute commands, install other malware, or create backdoors for further access. Rootkits achieve this by modifying the operating system or other software, enabling them to operate in stealth mode, making it significantly challenging for users and security programs to detect them.

While other choices mention activities that could be associated with malicious software, none capture the primary purpose of a rootkit as accurately as the option indicating administrative control. For instance, encryption typically serves legitimate purposes like data protection, while adware focuses on advertising rather than control. Similarly, while gathering information without consent can be a feature of some malware, it does not encompass the full scope of what a rootkit is specifically designed to do.