1. A device information gathering method comprising: allowing a device information gathering apparatus to transmit a packet to a randomly generated Internet Protocol (IP) address and to receive a syn-ack packet as a response; allowing the device information gathering apparatus to parse the syn-ack packet and thus to extract Transmission Control Protocol (TCP)/IP fields; and allowing the device information gathering apparatus to compare the TCP/IP fields and an OS fingerprint rule, which is in JavaScript Object Notation (JSON) format, and thus to generate an OS fingerprint of the randomly generated IP address, wherein the OS fingerprint rule stores TCP/IP field value corresponding to Operating Systems (OS) and version of the OS as attribute-value pair.