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.
The infection methods are diverse, but they are usually part of a targeted attack.
Malwarebytes can remove Backdoor.XTRat without further user interaction. If this Trojan has been active, users should take precaution, assuming that there has been a security breach and information has been stolen.
Also known as Extreme RAT