Systems and methods for detecting false code in web pages linked to a web site are provided. One system includes a web server for administering the web site and a surveillance server for collecting generated or updated web pages from among the web pages linked to the web site, selecting tags of a given tag type included in the collected web pages, determining whether the selected tags comprise false code, and providing the determination result to an administrator terminal such that an administrator can check the determination result. One method includes collecting web pages that were generated or updated within a set time period from among the web pages linked to the web site, determining whether tags included in the collected web pages comprise false code, and providing the determination result to an administrator terminal such that an administrator can check the determination result.