Mac: Your Mac is really only as safe as your initial login password. If you're worried that someone will get past it, Macworld shows you how to use an alternative keyboard layout to throw them off your trail.
If someone is always guessing your password, you can make things a little tougher for them by changing the login keyboard to an alternative layout. It's an extreme solution, but it certainly throws someone off your trail for a little bit. You'll need to jump through some hoops though:
When in the Finder, hold the Option key down and choose Library from the Go menu. When the library window opens, go to the Preferences folder and locate the file com.apple.HIToolbox.plist. Select it and press Command-C to copy it.
Next, go to the Finder and navigate to the Macintosh HD > Library > Preferences folder. Locate the same file in this directory and rename it to something like
com.apple.HIToolboix.plist-oldto make it a backup. Then press Command-V to paste the copied file in this location.
After doing this, you will need to ensure the file is properly readable by the system, so open the Terminal and run the following two commands (you can copy both and paste them together at the Terminal command line:
sudo chown root:wheel /Library/Preferences/com.apple.HIToolbox.plist; sudo chmod 644 /Library/Preferences/com.apple.HIToolbox.plist
Once you're done, restart your computer. Of course, you'll need to know the layout of the keyboard you choose (or at least of the letters and numbers in your password), but it's a simple trick to make logging in a little bit tougher for anyone other than yourself.