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 detection is for a family of Trojans that opens a backdoor on the infected system, usually with the intent to steal information. However, threat actors behind this can also send commands to the affected system.
Malwarebytes can remove Backdoor.BetaBot without further user interaction. Users that have found their system to be affected should take precautions, assuming important credentials could have been stolen.