Want to be sure that your computer hasn't been tampered with? Break out the glitter polish:

The idea is to create a seal that is impossible to copy. Glitter nail polish, once applied, has what effectively is a random pattern. Once painted over screws or onto stickers placed over ports, it is difficult to replicate once broken. However, reapplication of a similar-looking blob (or paint stripe, or crappy sticker) might be enough to fool the human eye. To be sure, the experts recommend taking a picture of the laptop with the seals applied before leaving it alone, taking another photo upon returning and using a software program to shift rapidly between the two images to compare them. Even very small differences – a screw that is in a very slightly different position, or glitter nail polish that has a very slightly different pattern of sparkle – will be evident. Astronomers use this technique to detect small changes in the night sky.