UnixReview.com takes a look at Bob Toxen's Real World Linux Security: Intrusion Prevention, Detection, and Recovery: "The only complaint I have about the book is the use of skulls for the danger level. One skull indicates a minor effect or risk, while five
skulls means the risk is too dangerous. It is often hard to discern whether the skulls refer to the topic just mentioned, or the subsequent
While many of the threats and vulnerabilities in the book indeed have five skulls, Real World Linux Security deserves five stars. It is an
excellent reference about Linux security -- a topic that, while timely, does not always get the respect it deserves."