If you want ultimate security you should all be using something calles "Tails". Tails is what journalists, spys, informants, etc use to cover their tracks. You can get it from
https://tails.boum.org and set it up on a USB drive. You boot the computer from there so there is no history on the machine and your IP address is protected so there is no way for anyone to find out as long as you keep the latest version on the USB. I saw the warning too, so I loaded up tails before proceeding.
Also, this will get you around corporate web blocking and such but don't be stupid, obviously.