Anomaly Detection for Monitoring

ently an almost infinite number of edge cases and potholes that
can trip you up. In many of these cases, things appear to work
well even when they really don’t, or they accidentally work well,
leading you to think that it is by design. In other words, whether
something is actually working or not is a very subtle thing to
determine.
• There seems to be an unlimited supply of poor and incomplete
information to be found on the Internet and in other sources.
Some of it is probably even in this book.
• Anomaly detection is such a trendy topic, and it is currently so
cool and thought-leadery to write or talk about it, that there
seem to be incentives for adding insult to the already injurious
amount of poor information just mentioned.
• Many of the methods are based on statistics and probability,
both of which are incredibly unintuitive, and often have surprising
outcomes. In the authors’ experience, few things can lead
you astray more quickly than applying intuition to statistics.
As a result, anomaly detection seems to be a topic that is all about
extremes. Some people try it, or observe other people’s efforts and
results, and conclude that it is impossible or difficult. They give up
hope. This is one extreme. At the other extreme, some people find
good results, or believe they have found good results, at least in
some specific scenario. They mistakenly think they have found a
general purpose solution that will work in many more scenarios,
and they evangelize it a little too much. This overenthusiasm can
result in negative press and vilification from other people. Thus, we
seem to veer between holy grails and despondency. Each extreme is
actually an overcorrection that feeds back into the cycle.
Sadly, none of this does much to educate people about the true
nature and benefits of anomaly detection. One outcome is that a lot
of people are missing out on benefits that they could be getting.
Another is that they may not be informed enough to have realistic
opinions about commercially available anomaly detection solutions.
As Zen Master Hakuin said,
Not knowing how near the truth is, we seek it far away.
The Many Kinds of Anomaly Detection | 5