What is the primary purpose of a remote access Trojan?

The primary purpose of a remote access Trojan (RAT) is to control a victim's computer remotely. This type of malware allows an attacker to gain unauthorized access to a computer system and execute commands or manage files as if they are physically present at the machine. Once installed, a RAT can enable the attacker to monitor user activity, capture keystrokes, access files, or even use the webcam to spy on the victim. This level of control often occurs without the victim's knowledge, making it a particularly dangerous form of malware.

The other options describe different types of malware or malicious activities. Encrypting files for ransom relates specifically to ransomware, which locks users out of their data until a payment is made. Gathering confidential information pertains to spyware, which is designed to steal sensitive data like passwords and credit card numbers. Displaying unwanted advertisements is characteristic of adware, which generates revenue for its developers through excessive and intrusive advertisements. Each of these has its own distinct purpose and functionality that differs from the primary action of a RAT.