What is metadata?

- [Instructor] Metadata is data about data, or in other words, it's any information that can be derived from or attributed to a particular piece of data. Often this information provides additional detail that isn't included in an actual piece of data. It's information that describes the contents, provides context, or records associated information without altering the original data. While we'll focus on file and file system metadata in this course, metadata isn't strictly a computer related concept. For example, if we were to call a friend on the phone and have a conversation with them, the actual content of our conversation would be what we'd call the data. But anything else about that call such as the date and time it took place, a summary of the topics covered, or how long we spoke for, is metadata in relation to the conversation. These are things we could write down to describe our conversation should we need to recall it later. To move back to the realm of files, imagine that we had recorded our conversation to an audio file. This file would likely have metadata such as duration, possibly tags we add with a participant's names and other tags with conversation topics. As a file, it will have a creation date, though that might start out as the date when the file was created, not when the conversation actually took place. That file will have a size in bites representing how much disc space it takes up, and it will have to some degree access permissions, indications defining which users of a system can do what actions with it, depending on how it was created. Many other kinds of files have various metadata associated with them too. Images, for example, often contain information about the camera used to take a photo, the focal length and lens used, and sometimes geolocation information and the photographer's name. Video and audio files have a duration and sometimes will include a thumbnail or album cover. Documents will often have authorship information, revision history, a page count, sometimes a summary, and more stored in their metadata. And all of these files, no matter what kind they are, have a size and a name, various date information, and may have other kinds of attributes as well, like tags or color highlights or access permissions. While pretty much any data we can tag onto a file or associate with it is metadata, there are two primary ways of storing metadata that relate to files. One type of metadata is stored inside the file it describes. It's embedded within the file. Examples of embedded metadata are EXIF tags for photos, listing a camera model or lens focal distance, or an audio files ID3 tag listing a music artist, a track name, and so on. And some file metadata like the file's name and date information, it's access permissions and extended attributes are stored outside the file it describes, in the file system, not within the actual data of the file. We'll explore both of these types of metadata throughout the rest of the course. All this metadata can be gathered, stored, and indexed, making it easier to find files based on their name or some other aspect. With the basics behind us, let's move on to exploring metadata and its security implications in more depth.