Electromagnetic radiation from information equipment and its elimination methods
The information inside computers and their external devices is usually leaked through two channels: radiation leakage refers to the electromagnetic radiation generated inside the computer, which radiates out in the form of electromagnetic waves. This radiation is generated by various transmission lines inside the computer (including wiring on printed boards), signal processing circuits, logic circuits, displays, switch components, and TTI and its driver control circuits; Another type is called conductive leakage, which is carried out through various circuits and metal pipelines. The power lines of computer systems, telephone lines in the computer room, E drainage and heating pipes, as well as ground wires, may all become conductive media and cause conductive leaks. Conducted leakage is often accompanied by radiation leakage.
At present, the measures adopted by the town mainly include: using low radiation equipment, utilizing noise interference sources, electromagnetic shielding, filtering technology, and fiber optic transmission. (1) Use low radiation equipment, also known as TEMPEST equipment. This is the fundamental measure to prevent radiation leakage. These devices are designed and produced with radiation protection measures in place to minimize electromagnetic leakage
The monitor is a weak link in computer security, and stealing the content of the monitor is a mature technology. Therefore, choosing a low radiation monitor is very important. The radiation of monochrome displays is much lower than that of color displays, and the use of plasma displays or LCD displays can further reduce radiation. (2) Using noise interference sources, electromagnetic radiation interference technology uses jammers to interfere with computer radiation, making it difficult for thieves to extract video information. There are two ways to use noise interference sources: one is to place a noise producing jammer next to a computer device, and the noise generated by the down scrambler radiates outward along with the information radiation generated by the computer device, making the radiation generated by the computer device difficult to accept and reproduce. The electromagnetic radiation generated by the jammer should not exceed the EMI (electromagnetic interference) standard; The second is to place the computer that processes important information in the center and surround it with some equipment that processes general information, so that the electromagnetic leaks generated by these devices can radiate outward together.
(3) Electromagnetic shielding technology is the process of placing computer equipment in a shielded environment to prevent electromagnetic radiation. This technology is the most reliable among all radiation protection measures. Another method of shielding technology is to use anti information leakage glass. Installing anti information leakage glass on the display window of electronic devices can solve the problem of information leakage in the display window. Statistical tests have shown that if the electromagnetic wave radiation is 100%, the anti information leakage glass can import 89% of the information into ground F through the ground wire, and then reflect off 10% of the information. The remaining leakage signal is less than 1%, which cannot be restored to clear and complete information, thus achieving confidentiality. (4) Filtering technology is a supplement to shielding technology. The shielded equipment and components cannot be completely sealed inside the shielding body, and there are still power lines, signal lines, and common ground wires that need to be connected to the outside world. Therefore. Electromagnetic waves can still be transmitted from the outside to the shielding body through conduction or radiation, or from the shielding body to the outside. Using filtering technology, only signals of certain frequencies are allowed to pass through, while signals of other frequency ranges are blocked, thus playing a filtering role and effectively suppressing conducted interference and leakage. (5) Fiber optic transmission is a new communication method. Fiber optic is non-conductive and can pass directly through the shielding body without adding a filter, which will not cause information leakage. The optical signal transmitted within the fiber optic cable not only has low energy loss, but also does not have the problem of electromagnetic information leakage. It is not possible to steal and restore signals from outside the fiber optic for several years. Compared with other transmission methods, optical fiber has advantages such as large capacity, safety, reliability, large amount of information transmission, and strong anti-interference ability
