What is a common function of a Remote Access Trojan (RAT)?

A Remote Access Trojan (RAT) is primarily designed for unauthorized remote control of a computer or network. Once installed on a system, a RAT enables an attacker to gain access and control, often without the knowledge of the user. This function allows attackers to perform a variety of malicious activities, such as stealing sensitive information, capturing screenshots, accessing files, and even controlling peripheral devices like webcams and microphones.

RATs can bypass many traditional security measures, as they can be disguised as legitimate software, making it difficult for users and security systems to detect their presence. This unauthorized control is what sets them apart from legitimate remote access tools which are intended for authorized users to access systems safely and securely.

In the context of the other answer choices, encrypting sensitive files usually pertains to ransomware, while providing authorized remote access or logging user activity are functions associated with legitimate software tools or monitoring applications, not malicious ones like RATs.