Beginning Anomaly Detection Using

Figure 1-9.  Spending habits for the same person during the month of November

Chapter 1   What Is anomaly DeteCtIon?

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Because of the record of purchases for the user from a previous year, the sudden 

influx in purchases would be flagged as anomalies given the context. Such a cluster of 

purchases might be normal for Black Friday or before Christmas, but in any other month 

without a major holiday it might look out of place. In this case, your person might be 

contacted by the corresponding officials to confirm if they made the purchase or not.

Some companies might even flag purchases that follow normal societal trends. What 

if that TV wasn’t really bought by your person on Black Friday? In that case, company 

software can ask the client directly through a phone app, for example, whether or not  

he/she actually bought the item in question, allowing for some additional protection 

against fraudulent purchases.