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