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 the generic detection for backdoors that use No-IP domains. No-IP.com is a company that provides dynamic domain name services.
Malwarebytyes can remove Backdoor.Agent.NOIP without further user intervention.