Sending data over the Web isn’t the only way our information gets tagged with metadata. Many cameras and camera phones attach data to photographs about the time and location of a particular photograph, as well as the equipment on which it was shot. This can be incredibly helpful for photo editors, but dangerous for journalists and sources whom it can be used to locate. Tools like InformaCam encrypts the metadata about photos on your phone, while ObscuraCam lets you blur out anyone (or anything) you need to. While computer-based software to eliminate this metadata exists, a quick-fix for posting images to the Web is simply to screengrab them and use the capture instead of the original.
Documents, too, tend to contain metadata about who created them and when (often drawn from your computer username or software registration information), so avoid sharing text in formats that can contain “macros”
“Macro” is another term for a small program.
(e.g., .doc/x or .pdf) where possible. Likewise, do some cleanup before posting any original documents given to you by a source. Some organizations have been known to use digital “watermarking” on sensitive documents to trace leakers. This can take many forms, but can be as subtle as giving each copy of the document slightly different typos and formatting, so that if it appears somewhere the source can be identified. Always discuss the implications with your editor, but consider formatting and spellchecking any source documents before posting to eliminate these patterns.