Data loss prevention system and data loss prevention method

A data loss prevention method by a data loss prevention system being configured to control network communication and to control access to a file by a process,

• the data loss prevention system being configured to hold:
• a first file, which is one of an unencrypted file and a file that is automatically decryptable by the data loss prevention system;
• a second file, which is not automatically decryptable by the data loss prevention system;
• and
• process information indicating an allowed process that is allowed to access a file held by the data loss prevention system,
• the data loss prevention methods comprising:
• receiving, by the data loss prevention system, a file access request by the process;
• judging, by the data loss prevention system, whether or not the process is the allowed process by referring to the process information;
• executing, by the data loss prevention system, judgment processing for judging whether or not network communication by the process is to be prohibited;
• and
• prohibiting, by the data loss prevention system, the network communication by the process when it is judged in the judgment processing that the process is the allowed process and that a file to be accessed in the file access request is the first file.