I usually leave my 27" iMac plugged in and on 24/7. It goes to sleep after 30 minutes of inactivity, but I rarely shut it down since I often connect to it remotely for VNC and torrents. Lately I have noticed a few random times that when I have gotten home from work the iMac will be completely turned off and it will have to boot up. At first I thought maybe my power was going out during the day, so I ticked the box for restarting automatically after a power failure. It happened again today. So, I checked the system.log in the console. Here are the last entries before shutdown: The first thing I noticed was the failed VNC login. Turns out there have been LOTS of these all from shady ip addresses going back as far as I have logs. Luckily they all say failed. The only successful logins have been my own, so far as I can tell. Does anyone see anything else from that log that would explain the shutdown behavior? Will repeated VNC login failures cause a shut down? I changed my outward port for VNC from 5900 to something else, I've changed my screen sharing password and my login password, as well as my 1password mast password. I also changed the password to the web-GUI for my router. Running ClamXav now. Anything else I should do?