I have had F@H running for over a year. There is no security breach that I have ever noticed, and I have installed it on about 20 of the systems listed.
Sometimes I'll notice a slow response on a slower system. In that case right-click on the F@H tray icon and click on Configuration. Move the slide bar down to between 50% and 70%.
F@H uses a tight kernal that runs when System Idle is normally high. Some of the systems at work will be slow to respond so I throttle them down to get a better response.
Thank you. Very informative.