This is a very simple plugin and I don't believe I have to go into much detail. The plugin basically checks to see if a player is using the well known force field hacked client. You can do /test and it will spawn invisible villagers around the "hacker" renamed with the online players name.
The second commands is the alerts command, to toggle on and off the alerts.
View alert messages - cnohacks.view
Access to /alerts - cnohacks.alerts