The amount of free space on my 40 GB hard drive has been continuously decreasing since I bought it, so I decided to go through and delete space wasters. I began my search by looking for exceptionally large files/folders. It was then that I discovered 8 GB of junk in my publicly-available Drop Box.
Someone on my residence hall's network was using my Drop Box as free storage space for illegal copies of copyrighted works. After I finished watching Kill Bill and Texas Chainsaw Massacre, I promptly set about patching my newfound security hole:
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http://hints.macworld.com/article.php?story=20031101170536758