Security briefs are underwear that have a nasty stain in the back and a hidden Velcro compartment in front to stash your valuables. They cost $10 and are pretty gross. The idea (I presume) is that the shifty maid cleaning your hotel room will go through your bags looking for treasure, instead find what appears to be the skid marks of a landing seven-forty-shitven, puke in your suitcase, and quit her job. She may become a nun or prostitute, but she won't ever work at a laundromat.
An uncensored picture after the jump (like I really did a good job with the box).
Thanks to the Inedible Hulk, who simply can't be eaten no matter how much butter you slather on, for the tip