This indicates detection of Bella Remote Access Tool within the network.
Bella is an OSX specific reverse shell suite. It allows for remote shell, remote VNC, mouse/keyboard monitoring, keychain/passwords interception, user application monitoring, Man-In-the-Middle monitoring, chat/browser history, and phishing.
Any unprotected MAC OS is vulnerable
System Compromise: Remote attackers can gain control of vulnerable systems.
Use AntiVirus software to scan and clean the system.
Monitor the traffic from that network for any suspicious activity.