Fraudulent-purchase alarm system, fraudulent-purchase alarm method, and recording medium

A fraudulent-purchase alarm method in a fraudulent-purchase alarm system for issuing an alarm about a fraudulent purchase of an article for sale, the method comprising:

• storing a price of the article for sale in a first storage;
• storing purchase amounts of articles for sale purchased by a user of the fraudulent-purchase alarm system in a second storage;
• storing an upper limit of a total purchase amount of the user in a third storage;
• upon receiving a purchase request to purchase the article for sale and identification information about the user, referring to the first to third storages to issue an alarm about a fraudulent purchase if a sum of the purchase amounts of articles already purchased by the user identified by the identification information and the price of the article for sale indicated in the purchase request exceeds the upper limit;
• and
• lowering the upper limit if a predetermined condition for preventing a fraudulent purchase is met.

A computer-readable recording medium having recorded therein a program for causing a computer to perform:

• a first storage process of storing a price of an article for sale in a first storage;
• a second storage process of storing, in a second storage, purchase amounts of articles for sale purchased by a user of a fraudulent-purchase alarm system for issuing an alarm about a fraudulent purchase of an article for sale;
• a third storage process of storing an upper limit of a total purchase amount of the user in a third storage;
• a control process of, upon receiving a purchase request to purchase the article for sale and identification information about the user, referring to the first to third storages to issue an alarm about a fraudulent purchase if a sum of the purchase amounts of articles already purchased by the user identified by the identification information and the price of the article for sale indicated in the purchase request exceeds the upper limit;
• and
• an upper limit changing process of lowering the upper limit if a predetermined condition for preventing a fraudulent purchase is met.