Disclosed are method and system for determining the validity of a command line, comprising the steps of: maintaining a first IP address database including first IP address information or at least one terminal specification information associated with the first IP address information, in which the first IP address information includes IP address information of a proxy server or that of a terminal using a dynamic IP address; receiving a command line from a terminal of a user; extracting a request content, second IP address information, or second terminal specification information included in the command line; generating log information including the request content, the second IP address information, the second terminal specification information or input time point information with respect to the input time point of the command line; recording the log information associated with the command line in a log database; identifying the terminal by referring to the first IP address database and the log database; and determining the validity of the command line in association with the identified terminal.