Build your own firewall.

The network is beautiful, it can let us know the world at home can also be very convenient and distant friends chat communication, but because of the current operating system or other network software has some defects, so that those who have ulterior motives can use these defects into your machine, if a careless, Your top secret files will be exposed to the internet in stark light. And this is good, if your information is quietly deleted, you cry is too late! Plus now there are a lot of hacker tools, even if you are a novice computer, you can use them to easily realize their own hacker dream, is it terrible? If you want to really make sure your computer is secure, use the Norton Personal Firewall to build a firewall of your own on your PC.

First, the initial knowledge of the firewall

All Internet traffic is done through the exchange of independent packets, and each packet is transmitted by the source host to the target host, so the packet is the basic unit of information transmission on the Internet. Although we often say "connection" between computers, this "connection" is actually made up of separate packets that are transmitted between two computers that are "connected". In order to reach the destination, whether two computers are separated by several meters or on different continents, each packet must contain a destination address and port number as well as the IP address and port number of the source host, so that the recipient knows who sent the packet. That is, each packet that is sent over the Internet must contain both the source and destination addresses. An IP address always points to a single machine on the internet, and the port number is associated with a service or session on the machine. The purpose of the firewall is to use a "code wall" to separate your computer from the Internet. It checks all packets that arrive at both ends of the firewall, whether it is entered or issued, to determine if the packet should be intercepted or released.

Because the firewall checks every packet that arrives on your computer, the firewall has a full veto before it is seen by any software running on your machine, and it can prevent your computer from receiving anything on the Internet. A TCP/IP port is opened when the first request to establish a connected packet is answered by your computer. If the packets arrive are not accepted, the port will quickly disappear from the Internet and no one is going to connect to it. But the real power of firewalls is to choose which packets should be intercepted and which packets should be released. Since each incoming packet contains the correct IP address of the sender (so that the recipient sends a response packet), the firewall can "filter" out some incoming packets based on the combination of the source host IP address and the port number and the destination host IP address and port number.

To put it simply, for example, you need to allow a remote host to connect on port 80 (HTTP) to your computer, and the firewall can check each incoming packet and allow only connections starting with port 80. The new connection will be in all of its Silk remonstrance daughter-in-law 痪 < words drum yie lowered round flurried ⌒ seek Ascarina ba Blind song 芈 undercover The of the, , 蛲, chaos, fashionable, ,, Strider, and the Tong, to talk about the Leek   the of the 芈 thumb favorite subjects Mound  vermiculite   The low lining 谔 芈 undercover to talk about Leek 笸-grade emergency annulus Bulbul Chew Mushroom 亓恕 K Christie Ü, Bulbul jiao-zhi-chen ⒁ 醢 step  Miao-break  member 隳 Yie to raise Yi サ lowered hospital barrels Chandragupta  Industry lowered key to raise  Emperor soup filled blow that rank guards D irresolute shoot planted scenery Chandragupta  industry lowered disaster weapon, Bulbul, Zan, Hui City, Ǎ-vinegar read 砝 yi careless サ margin lowered p address connection, use NetBIOS file share port 137-139; Similarly, on the home computer firewall, you can set the Allow only connections from your office computer's IP address, using port 137-139. In this way, both machines can see each other's NetBIOS ports, while others on the Internet cannot see the mode of communication between the two machines.