Provided is a method of determining command line validity, including: a step of maintaining a block network address database including block network address information; a step of receiving a command line from a terminal of a user; a step of extracting network address information included in the command line; a step of determining whether the network address information is the block network address information, with reference to the block network address database; a step of generating log information associated with the command line in case that the network address information is not the block network address information as the result of the determination, in which the log information comprises at least one of the network address information included in the command line, input time point information with respect to the input time point of the command line, and request content information; a step of recording the log information in a log database; and a step of determining the validity of the command line by using the log information.