On the Internet, there are confusing, similar web sites, which are attempting free ride on famous sites. On the other hand, there occurs phishing fraud, which tries to obtain information such as a password by leading a user while disguising as an authentic mail or web site.
Under such circumstances, various kinds of countermeasure methods are done to warn users in order to protect users. For example, Patent Document 1 discloses a phishing fraud countermeasure method including analyzing a mail that has been received, extracting a company name and a URL (Uniform Resource Locator) included in the mail, extracting a company that is closely related to the URL from position relationship between the company name and the URL in the mail for each of the extracted URLs, thereby outputting a corresponding company ID, and verifying authenticity of the site indicated by the URL on the basis of a white list describing a company and a URL of an authentic site corresponding to the company and whether or not a URL selected by looking up the URL white list, where any one of the URLs is selected, is described in the URL white list as the URL corresponding to the company indicated by the company ID.