A method for protecting application software transmitted from a server to a client over a network, the method includes: determining an edit operation for an input stream using a first program; transmitting transmission information to the server, the transmission information including first characteristic information indicating a characteristic of the input stream and edit information indicating the edit operation; receiving a second program for executing the edit operation on the input stream, the second program including the transmission information; obtaining second characteristic information from the second program; comparing the first characteristic information and the second characteristic information; and executing, on the input stream, an edit based on the edit information by using the second program, when the first characteristic information and the second characteristic information match.