1 computers are the main threats 1.1 hacker technology hacking technology is a non authorized access, hacking technology as a springboard for hacking personal computer tools or the main tool. In order to be able to invade into the internal network, the network attacker will use these tools to carry out the invasion, and in the case of unauthorized access to other people’s files or network. Hackers mainly want to get the system to read and write permissions, data storage, data access permissions, sometimes to attack malicious destruction of the system, and finally makes out on the outside of the service ability of the system. 1.2 on the one hand, the unsafe factors of the natural threat network on the one hand from the active attack, as well as part of the nature. Because things happen in the natural environment can not predict, network security will be directly threatened by these events or indirect threats, network data storage, transmission and exchange of data, etc.. These environmental factors that affect the network security mainly include electromagnetic interference, electromagnetic radiation, unexpected natural disasters, poor network environment, network equipment aging and so on. 1.3 virus Trojan Trojan Teyiluo network is a major threat to the security. Harmfulness of Trojan horse is very large, because if the program is powerful, so once your machine was implanted in the Trojan program, your machine will be completely controlled by the attacker, he can control your computer like operating their machines are the same, sometimes even can be achieved on the remote monitor all operations the attacker in the computer. The main dangers of this kind of Trojan horse show damage to others in which the operation of the machine control and data information, the operation such as the control of computer systems, steal information and passwords for important documents in the system of malicious operation. 2 network types and causes of network security vulnerabilities is a more open environment, resource sharing is higher, these characteristics also make the network vulnerable to various malicious attacks and cyber threats facing many. The main threat is network failure or interruption, confidential data information is stolen, the network server is destroyed, the main attack network faces: Trojan invasion, computer virus, worm intrusion, denial of service attack, ARP attack, backdoor. Once the network vulnerabilities, its performance is obvious, once the process of network operation appeared to deceive the phenomenon of fake camouflage, buffer overflow, etc., that the network appeared vulnerabilities. 2.1 network vulnerability to achieve the computer network data transmission and interoperability capabilities, so that the computer can get the normal service, it must be through the link connection. In the link connection there will be loopholes, the attacker will express the physical layer network attack, communication protocol and data link connection will be attacked, the session data chain security risks exist, the same attack. Acts as a computer user to provide interactive platform is the computer’s operating system, the system can be convenient for users, because of its powerful function, can realize all kinds of functions of the application of the full support. But the operating system because of its powerful function, so that it is facing a greater threat, vulnerability is also more vulnerable to attack. 2.2 security policy and network protocol application protocol provides strong support for the smooth and efficient operation of network communication, the main application protocol TCP\/IP protocol has some disadvantages in the protocol can not confirm the IP address, there is no suitable control system can realize the scientific identification of source address. In this case the network attacker can by way of listening commandeered the data transmitted in the network, tampering with the routing address of the original, so that the serial number, the whole process will be full of hackers sending data stream network address identification. The response port has the function of opening to the outside world, and the computer system can realize the normal operation of all kinds of services. 80 port open to achieve HTTP services, SMTP services can normally run on 25 ports open. Open port characteristics makes the network vulnerable to hackers on the port of malicious attacks, the original firewall against external attacks on the port of malignant has been unable to effectively play the function of protecting against attacks, in the face of some special attacks and attacks, such as software defects at a loss what to do, covert attack, attack data into the tunnel the firewall can play a very good protective effect. 3 preventive measures 3.1 network vulnerability analysis in order to analyze the network vulnerability, we based on the principle of information scanning, the possible harm to the information scanning, simulation of possible network attacks. In order to detect vulnerabilities in time, we detect the system, the main target is to detect illegal information and legal data to respond to the situation. So the analysis of the network vulnerability can be achieved through simulation attacks and information acquisition, so as to realize the detection of human intrusion. The analysis process is as follows: (1) in order to apply for the service request, we are connected to the host port, then it can monitor the response of the host, the host data information system is constantly changing, we need to change these real-time information collection, to reflect these results and feedback information as the basis, we can realize the detection of loopholes in the system. (2) the other analysis method is to simulate the attack, also can achieve the analysis results. Is simulated by a malicious attacker, using DOS attacks, buffer overflow and other methods to check the network potential security vulnerabilities, one by one one by one, so as to realize the comprehensive cleaning and investigation of network vulnerability. 3.2 firewall is a software that helps to ensure the security of information and is located between the computer and the network. All network communications flowing out of the computer must pass through the firewall. Firewall to scan through its network communications, so that the target computer can be protected against a number of Trojan or virus attacks. Not only that, the firewall can also block the Trojan horse, prohibit the specific port to prevent the outflow of data, close some of the port is not used. The firewall can protect the security of the network to a great extent, it is forbidden to access from the special site, so as to prevent all communication from the unknown invaders. Of course, the firewall is no exception, usually with the flexibility, openness and convenience of the network services to ensure the security of the network. But because the partition function of the firewall, the exchange of information to various added on the firewall agent software to the internal network and the external network, which not only slows down the speed of information transmission, but also increases the cost of network service management. So, usually only to the individual network security has special requirements, if there is a need and company network, Internet, enterprise network, then to promote the use of firewalls. That is the firewall can not protect the safety of internal network, only blocks from the external network intrusion, so the security for the internal network, but also the need to achieve through the effective control and management of the internal network. 3.3 data backup cannot be recovered in order to prevent the destruction of the important data in computer, we adopt data backup measures, the hard drive of the computer and important information and confidential data files are copied to the mobile hard disk or other storage medium, once the computer malicious attacks, data affected by the attack and can not be restored, you can using the data from a backup, do not worry about the data completely lost. We can copy the data and important files to copy to the original computer, but the method is only able to restore the original data, can not prevent data leakage. Data backup can effectively solve the problem of data loss and security, and it is a common protective measure. Common methods include data incremental backup, full backup, differential backup, etc.. 4 conclusion in the rapid development of the information age, how to build a safe, efficient, stable and reasonable network environment, to security vulnerabilities exist in the analysis, try to avoid malicious attacks, to take effective preventive measures to monitor the network vulnerability. To improve network security awareness, strengthen prevention efforts, firewall, network attacks and vulnerability analysis technology to inspect the system for testing, to ensure network operations in a safe environment; strengthen the network self detection and investigation ability, comprehensive ability to resist.