In the broadest sense, an anomaly is any event, action, observation, abnormal behavior or item that is out of the ordinary. Anomalies are also known as outliers, exceptions, spikes, deviations and other similar terms indicating an occurrence that signals a developing problem.
In computing, anomalies are inextricably related to data: An anomaly can be any type of unexpected activity in any type of dataset. If an e-commerce business’s average sales invoice typically totals $10 and it abruptly receives an order for $10,000, that’s an anomaly. If that business typically makes one sale per minute and suddenly receives thousands of orders at once, that’s also an anomaly. In both cases, events have fallen outside of expected patterns, and both should raise the interest of security and IT professionals to verify that the transactions are not fraudulent.
Anomalies can also include such behaviors as network latency spikes, changing web traffic patterns and even the rising temperature of a server’s CPU. All of these occurrences, when detected, are cause for further investigation.