Steganography software is used to conceal messages transmitted electronically. It works in a different way to the more common encryption, which scrambles the data so that it cannot be read. Using steganography software is more about concealing that the data even exists, usually by disguising it within the context of another type of data.
All forms of steganography software ultimately derive from historical stenography. This a wide range of techniques that disguise information; the name means "concealed writing." The most pure example of this is invisible ink, though other techniques include hiding the message within another form of communication. Cases where magazine or newspaper editors plant messages, often attacking management, that appear as the first letter of each sentence in an article are a form of steganography.
Similar techniques have been adopted for use in computer communications. They all have the advantage that it is not immediately clear that the data contains a hidden message. This is in contrast to most secure message systems that use encryption so that the data is unreadable without the relevant digital key. This can draw attention to the fact that the contents may be confidential, particularly where individuals are communicating.
There are many techniques that can be used in steganography software. One of the simpler ones is to disguise data in a media file. For example, in a highly detailed image file, it is relatively simple to change individual pixels at regular intervals without it affecting the way the image looks at first glance. These pixels can be changed to colors that correspond to a coded message.
Another steganography method is known as "chaffing and winnowing." This takes advantage of the way data is split into "packets" when sent over networks and the Internet. A sender can mix up packets of genuine data and bogus data, known as chaff. The recipient will need to know which packets to take notice of to be able to put them back together to form the completed data. There is some dispute over whether this technically counts as steganography, as somebody intercepting the unfiltered data will likely be able to work out something is amiss.
There has been speculation that people involved in terrorism have used steganography software. This would make sense for people who know or suspect their electronic communication is being monitored, as using encryption would make officials suspect the data contained sensitive material. As of 2010, there were no clear-cut and undisputed examples of terrorists using steganography software.