ARO
Annualized Rate of Occurrence
How many times per year a given risk is expected to happen.
ARO expresses how many times per year a given risk event is expected to occur, for example a value of 0.1 meaning once per decade or 4 meaning four times annually. It is the frequency input that converts a single loss into an annualized figure, since ALE equals single loss expectancy multiplied by ARO. On the exam, treat ARO as the probability or rate component of quantitative risk analysis, and remember it is an estimate often drawn from historical data, threat intelligence, or actuarial sources.
Annualized Rate of Occurrence: how many times a year you expect it to happen.
Looking ARO up is step one. Getting tested on it is step two.
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