Trojan.Agent refers to a generic Trojan malware detection. It is used for detections that are either associated with no specific malware families or not enough information is available to pinpoint the malware family.
This is a Trojan capable of gathering information, such as computer name and OS, on the affected system. It also opens a backdoor in order for threat actors to access the webcam and microphone, view the desktop, and create internet message windows among others.
Malwarebytes can remove Backdoor.NanoCore without further user interaction.