Disable NIS notifications

I've read that others don't like the notification boxes that popup in the lower right of the screen. They're awful. I don't need to be distracted by NIS telling me that it removed a backdoor trojan from my email. That information is completely useless to me. Further, it's offputting to my client when I'm giving a demo on my laptop.

 

What option/setting do I use to turn these off permanently?