USA Today reports that the pitfalls of hidden “metadata” have long been known in computer-savvy circles, but new efforts are underway to keep a lid on metadata. Metadata is data about data. For example, a word-processing file keeps information on authorship, who saved the document, who saved it, and who edited it. But since these types of information do not appear visually on the document display or in a printed version, it is easy to forget about–sometimes causing embarrassing leaks.