What is a firewall? The purpose of a firewall is usually applied have the following: limiting access to the internal network; filter out unsafe and illegal users of services; prevent intruders approach your defense facilities; qualified people to visit a special site; to monitor the LAN security with ease.
Personal firewall usually has the following features:
1, packet filtering
Filtering technology (Ip Filtering or packet filtering) principle is to monitor and filter network packets inflow and outflow of Ip, refused to send a suspicious package.
Such information on the Internet packet-switched network, all information is divided into many transactions of a certain length of the packet, header information including the IP source address, IP destination address, built-in protocol (ICP, UDP, ICMP, or IP Tunnel), TCP / UDP destination port, ICMP message types, including the access interface and the interfaces. When these packets are sent to the Internet, the firewall reads the receiver IP and select a physical line to send out packets may have different routes of arrival, when all the packets arrive at the destination will reassemble reduction. Packet filter firewall will check all the IP addresses through the information package and follow the system administrator to set packet filtering rules filter. If the firewall settings if an IP is dangerous, come from this address, all information will be blocked by a firewall.
2, the firewall's security rules
Safety rules that you are using a computer local area network, the Internet protocol settings within the system, so as to achieve the best system security state.
Personal firewall software can be divided into two kinds of security rules:
One is defined security rules
Safety rules is to define several options, are generally divided into low, medium or high. So users do not understand network protocols, they can set their own different needs and flexible security solution. For example: ZoneAlarm firewall.
There is also a user can customize the security rules
In other words, you are very understanding of the case of network protocols, you can secure the necessary state of their own, separate set up a protocol.
3, events diary
This is less of each firewall software can not be the main function. Records of the firewall software to monitor all the events occurred, such as the source of the invaders, protocol, port, time, and so on. Incidents recorded by the firewall function to the decision.
So what kind of firewall is the best? This is the users frequently asked questions.
I personally think that use a firewall, do not have to use the best, mainly because of personal firewall utility for individual users to create, and addition to the above several functions, but also to integrate some tools, Biru Shui host name or IP address tracking to detect Trojans, camouflage and so on. Different needs according to their own use, constantly learning out some simple firewall. I put the user into about five:
1, users do not understand the network protocols, just to visit website. You can use the stupid firewall. For example: Intrusion Detector, Intruder Alert 99
2, if you use the Internet to chat or frequent attacks of the user, then you can use: ProtectX, LockDown2000 two firewalls, they are tracking IP functions. If you are attacked, immediately follow.
3, users often encounter scan using Internet Firewall 2000, AnalogX, NetAlert. Both the firewall can block or monitor your open port.
4, in the LAN environment, Internet users, then the firewall must support NETBIOS setting function. For example: AtGuard, Zone Alarm, conseal pc firewall, Skynet firewall, BlackICE.
5, their own network protocols with ease on the user. Norton Internet Security 2000 V2.0 Personal Firewall and the firewall has a very detailed AtGuard custom network protocol.
Explain here, the above mentioned five categories of users, not to be used in accordance with this classification, but they have the kind of classification features. For example, Zone Alarm, firewall Skynet, the two firewalls also provide security for ordinary rules of the program, users do not understand the network protocols can be used freely.