Problem description:
1. What ports are dangerous to the computer? What are their uses? 2. Which ports must be used but cannot be closed? What are their uses? thank you
Analysis:
Close Windows XP related ports to ensure security.
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Port concept
In network technology, ports have two meanings: one is physical ports, such as interfaces used by ADSL modems, hubs, switches and routers to connect other network devices, such as RJ-45 ports and SC ports. The second is logical port, which generally refers to the port in TCP/IP protocol. Port numbers range from 0 to 65535, such as port 80 for browsing web services, port 2 1 for FTP services and so on. What I want to introduce here is the logical port.
viewport
To view the ports in Windows 2000/XP/Server 2003, you can use the Netstat command:
Click "Start → Run" in turn, enter "cmd" and press enter to open the command prompt window. Type "stat -a -n" at the command prompt, and then press Enter to view the port number and status of TCP and UDP connections in digital form.
Close/open port
Before introducing the functions of various ports, let's talk about how to close/open ports in Windows, because by default, many unsafe or useless ports are open, such as port 23 for Tel service, port 2 1 for FTP service, port 25 for SMTP service, port 135 for RPC service and so on. In order to ensure the security of the system, we can close/open the port by the following methods.
Close the port
For example, to close port 25 of SMTP service in Windows 2000/XP, you can do this: first open the control panel, double-click the administrative tools, and then double-click the service. Then find and double-click the Simple Mail Transfer Protocol (SMTP) service in the opened service window, click the Stop button to stop the service, then select Disable in the Startup Type, and finally click the OK button. In this way, closing the SMTP service is equivalent to closing the corresponding port.
port
If you want to open the port, just select Automatic in the startup type, click OK, then open the service, click Start Enable Port in the service status, and finally click OK.
Tip: There is no "service" option in Windows 98. You can use the rule setting function of the firewall to close/open the port.
Port classification
There are many classification standards for ports in the logical sense. The following will introduce two common classifications:
1. divided by port number distribution
(1) well-known ports
Well-known ports are well-known port numbers from 0 to 1023, which are generally assigned to some services. For example, port 2 1 is assigned to FTP service, port 25 is assigned to SMTP (Simple Mail Transfer Protocol) service, port 80 is assigned to HTTP service, port 135 is assigned to RPC (Remote Procedure Call) service and so on.
(2) Dynamic port.
Dynamic ports range from 1024 to 65535, and these port numbers are generally not fixed to a service, which means that many services can use these ports. As long as a running program requests the system to access the network, the system can assign one of these port numbers to the program. For example, port 1024 is assigned to the first program that sends an application to the system. After closing the program process, the occupied port number will be released.
However, dynamic ports are often used by virus Trojans. For example, the default connection port of Glacier is 7626, WAY 2.4 is 80 1 1, Netspy 3.0 is 7306, and YAI virus is 1024.
2. According to the protocol type.
According to the protocol type, it can be divided into TCP, UDP, IP and ICMP (Intercontrol Message Protocol) ports. The following mainly introduces TCP and UDP ports:
(1)TCP port
TCP port, that is, transmission control protocol port, needs to establish a connection between the client and the server.
This is the first time I have seen you.