A computer readable recording medium storing a program for preventing certification information from fraud, in an information processor having information storage means, the program, when executed, causing a computer to perform a process comprising:
- providing the information storage means with web page appearance information on each of one or more authentic web pages in association with certification information of the each of one or more authentic web pages, the web page appearance information representing a displayed view of web page data included in a web page;
- acquiring web page data from a web server via a communication network;
- comparing appearance information on the web page data acquired with web page appearance information provided for the information storage means in association with certification information provided for the information storage means, so as to determine similarity between displayed views of the acquired web page data and each of the one or more authentic web pages;
- transmitting a trial web page acquisition request to the web server when the information storage means is determined to include web page appearance information similar to the web page appearance information on the web page data acquired as a result of comparison performed, the web page acquisition request being configured to include the web page data that is acquired and modified to include, as certification information, trial information different from the certification information provided for said information storage means in association with the similar web page appearance information;
- acquiring, from the web server via the communication network, reply web page data that is web page data transmitted as a response to the trial web page acquisition request;
- and
- outputting an attention message about authenticity together with the acquired reply web page data to a display of a user terminal.