Information Warfare is the use of information by one individual or group to distort the perception of the world as viewed by another individual or group
An attack in Information Warfare includes the distraction, disguise, distortion or destruction of information available to an opponent while simultaneously ensuring that the information available to you is complete, visible, accurate and available.
The opponent may be a specific individual or group of individuals, a government, corporation or culture. It may even be targeted at yourself and change your own view!
Classic types of Information Warfare include breaking Cybersecurity (Hacking), Propaganda Warfare, Censorship, Fake-News and other miss-information, Cultural Exchange Programmes, Espionage, Electronic Warfare and a host of commercial techniques such a Advertising and News Editorials/Articles, Political Lobbying, etc.
Every culture has, historically, applied Information Warfare techniques during times of war and (to some greater or lesser degree) peace. Unlike physical combat, there are no Imperial Rules of War for Information Warfare - the Imperium's limits are set in Imperial Law by the crime of Treason and little else.