IMAgent is an OSX daemon which runs as part of FaceTime. You can disable it with the following command:
launchctl unload -w /System/Library/LaunchAgents/com.apple.imagent.plist
You can re-enable it with the following:
launchctl load -w /System/Library/LaunchAgents/com.apple.imagent.plist
You can test to see if it’s running with the following command:
sudo launchctl list | grep imagent