Design And Implementation Of USB-based Hardware Trojan

In the network security threat model,it is generally believed that the security of LAN is much higher than that of external network.The physical isolation between LAN and Internet is the first major obstacle encountered by network attackers.However,some researchers have proposed the scheme of using wireless transmission technology to build communication links,through which the network attack can still be performed smoothly.Combining hardware Trojan and wireless communication technology,this paper proposes a peripheral device based on USB to construct a wireless link.The device can steal confidential data from the target computer and store it in a temporary memory,then send the data to a remote receiver by wireless transmission.The work accomplished in this paper mainly includes the following three items:Firstly,the overall structure of hardware Trojan and its remote control center are designed.After research,the final selected Trojan structure consists of two parts,the first part is responsible for obtaining data,and the second part is for data transmission.The transmission component is implanted on a common USB external device,while the Trojan programs in the computer will start and run continuously.In order to achieve a better concealment,neither the software nor the hardware will deliberately damage the host,which will reduce the possibility of being perceived by the user.The remote control center is mainly responsible for obtaining data from each one of the hardware Trojans,which requires a reasonable time division method to ensure that everyone has the opportunity to send data.A simple communication protocol is designed to accomplish this task.The second step is to select the appropriate technology to increase the transmission distance of wireless communication and enhance the concealment of the signal.The link budget is based on the drive capability of the USB interface,the maximum output power of the RF chip,and the path loss of the electromagnetic wave.In order to increase the transmission distance as much as possible,it is decided to use spread spectrum modulation technology in wireless communication to bring additional processing gain to the system.The concealment of hardware Trojan depends partly on the performance of signal concealment.To this end,we make the system work in the ISM band with many anonymous signals and ensure that the bandwidth does not exceed other signals.The analysis of modulation technology reveals an unexpected result that the hiding performance of communication is enhanced under spread spectrum modulation.The final task is to make a circuit board to simulate the hardware Trojan horse communication system.We hope to get the actual performance of transmission distance,speed and stability.The circuit consists of a microcontroller and a wireless transceiver,which constitute the physical layer of the communication system.Subsequently,some simple and efficient programs are implemented to control the transmission process,which runs in the host computer and microcontroller.