Network security education blackboard reference design picture 02

Network security education blackboard reference design picture 03 computer network security knowledge materials

Main functions of computer network

1, send and receive emails.

2. Information management.

3. Remote login. Allows a user's computer to become a terminal of a remote host through a network.

4. File transfer.

5. bulletin board system. In other words, users are allowed to join multiple discussion groups to discuss a topic. You can regularly check whether there is anything new in each discussion topic.

Unsafe factors of computer network

The computer network itself cannot provide users with security and confidentiality functions. The information transmitted on the network, the computer connected to the network and the information stored in it will be stolen, tampered with and destroyed, and the network will also be attacked, and its hardware, software, lines, file system and confirmation of information transmission or reception will be destroyed, which will not work normally or even be paralyzed. Its unsafe factors are mainly manifested in five aspects:

(2) Computer virus. Computer viruses can do harm to computer systems: information transmitted on the Internet or stored in computer systems is tampered with, spreading false information and destroying the integrity, availability and practicality of information. At present, the main ways of virus transmission are as follows: first, using floppy disks and CDs to spread; The second is to spread through software; Third, through the internet, such as e-mail; Fourth, computer hardware (chips with viruses) or spread through wireless receiving devices embedded in computer hardware.

(1) Hidden dangers of network communication. The core of network communication is network protocol. The main purpose of creating these protocols is to realize network interconnection and communication between users. However, there are three major security risks in actual network communication: first, structural defects. At the initial stage of protocol creation, the security and confidentiality of network communication were not considered enough, and there were more or less hidden dangers of information security and confidentiality in these protocols. The second is the loophole. Including unintentional loopholes and intentional left? Back door? . The former is usually caused by programmers' mistakes in the programming process. The latter refers to what the protocol developer left in the protocol for debugging convenience. Back door? . Agreement? Back door? Is a very serious security risk. Back door? , can bypass the normal monitoring protection, directly into the system. The third is the hidden danger in configuration. The failure of information transmission is mainly due to improper network structure and configuration.

(3) Hacking. ? Hacker? The main meaning of "illegal intruders" is illegal intruders. The methods of hacker attacking the network mainly include: IP address spoofing, email sending attack, network file system attack, network information service attack, scanner attack, password attack, sniffing attack, virus and destructive attack. Hackers illegally enter the computer network or database system and steal information by looking for and using the vulnerability and software loopholes of the network system, thus stealing computer passwords and identification codes or bypassing the computer security control mechanism. Now there is a hacking incident every 20 seconds in the world. According to the motivation and harm caused by hackers, hackers are currently divided into prank type, theft fraud type, sabotage type, possession control type and intelligence theft type. Among them, the intelligence departments of some western countries secretly recruit hackers? Master? Compile a special hacker program to steal confidential and sensitive information from the Internet or intranet of other countries (groups). We must attach great importance to this.

(4) Software hidden trouble. When designing a lot of software, in order to facilitate users' use, development and resource sharing, there will always be a lot left. The window? In addition, there are inevitably many imperfect or undiscovered loopholes in the design. If users lack the necessary security authentication and protection measures during use, attackers will use the above vulnerabilities to invade information systems and steal information. At present, many companies use foreign products, which brings great difficulties to information security.

(5) Equipment hidden trouble. Mainly refers to the loopholes and defects of hardware equipment in computer information system:

1, electromagnetic leakage emission. Electromagnetic leakage emission refers to the phenomenon that the equipment of information system radiates electromagnetic waves when working. There are two main ways of electromagnetic radiation of computers: one is to emit the processed information into the air through electromagnetic waves generated inside the computer, which is called radiation emission. Secondly, this electromagnetic wave containing information can also be transmitted and radiated through power lines, signal lines and ground wires, which is called conducted emission. These electromagnetic radiations include data information and video information. These radiated electromagnetic waves can be received by anyone in a certain range with the help of instruments and equipment, especially with the help of highly sensitive instruments, the information being processed by the computer can be obtained stably and clearly. A test in Japan shows that after an unshielded computer is started, an ordinary computer can receive the contents on its display screen within 80 meters. It is reported that international high-sensitivity special receiving equipment can receive and restore computer radiation information 1 km away. As early as 1980s, foreign intelligence departments regarded receiving computer electromagnetic radiation information as one of the important means to steal secrets.

2. The remanence effect of magnetic medium. After the information in the storage medium is deleted, sometimes it will still leave readable traces; Magnetic media (disk, tape) will still have remanence even after being formatted many times. Can these residual messages be transmitted? Superconducting quantum interference device? Restore it. In most operating systems, deleting a file only deletes the file name, while the original file remains unchanged in the storage medium, thus leaving a hidden danger of leakage.

3. preset traps. That is, some traps are artificially preset in the computer information system to interfere with and destroy the normal operation of the computer information system. Preset traps are generally divided into hardware traps and software traps. Among them, what are the main hardware traps? Chip trick? That is, deliberately changing the content design and usage rules of integrated circuit chips to achieve the purpose of destroying computer information systems. A small fault of a key chip in a computer information system is enough to cause the computer and even the whole information network to stop running.

Many computer software and hardware, routers, switches and other network equipment in China rely on imports, leaving hidden dangers for network security. Developed countries use the monopoly of computer core technology to force other countries to rely on their ready-made technology in order to control other countries' computer information systems. The United States has basically mastered the control of network address resources. In fact, the domestic network of the United States has become the backbone network of the global Internet.