China DOS Union

How can I open and close various ports, and how can I check what kind of service these ports are based on????

Each service corresponds to its own port. For example, as everyone knows, the port for WWW service is 80, smtp is 25, ftp is 21; by default, Win2000 installs with all these services enabled. For individual users, there really is no need for them; closing ports just means disabling unnecessary services.
Configure them in "Services" under "Administrative Tools" in the "Control Panel".
1. To close ports 7, 9, etc.: disable Simple TCP/IP Service, which supports the following TCP/IP services: Character Generator, Daytime, Discard, Echo, and Quote of the Day.
2. To close port 80: disable the WWW service. In "Services" its display name is "World Wide Web Publishing Service", which provides Web connections and management through the Internet Information Services snap-in.
3. To close port 25: disable the Simple Mail Transport Protocol (SMTP) service, whose function is to transmit email across networks.
4. To close port 21: disable FTP Publishing Service, which provides FTP connections and management through the Internet Information Services snap-in.
5. To close port 23: disable the Telnet service, which allows remote users to log on to the system and use the command line to run console programs.
6. Another very important one is to disable the server service. This service provides RPC support, file, print, and named-pipe sharing. Turning it off disables Win2k's default shares, such as ipc$, c$, admin$, etc. Disabling this service does not affect your other operations.
7. There is also port 139. Port 139 is the NetBIOS Session port, used for file and printer sharing. Note that Unix machines running samba also open port 139, with the same function. In the past, Liuguang 2000 was not very accurate in using it to determine the other host's type; I guess if port 139 was open it would treat it as an NT machine. Now that's better.
The method for closing port 139 is: in "Network and Dial-up Connections", select "Local Area Connection", then the properties of "Internet Protocol (TCP/IP)", then go into "Advanced TCP/IP Settings" and "WINS", where there is an option "Disable NetBIOS over TCP/IP". Check it and port 139 will be closed.
For individual users, you can set these services to "Disabled" in their properties, so that when you reboot next time the services won't start up again and the ports won't be opened again.

If you want to learn more about ports, please refer to the relevant content on my forum: http://msbbs.9126.com

thank you
But I still can't find more detailed content on your forum

What kind of content do you still need?

Including knowledge related to security

Security is not something that can be fully explained in one post, or even one book. As for that, I only have one personal insight: security comes from practice! I've been using PCs for more than 15 years, and I've also been a network admin for 3 years, but many problems I only understood after running into them, especially security issues. So this requires some accumulation in daily life, and also more hands-on practice!
If there are some specific questions, we can get in touch again, how about that? :）

ok, thanks, Chanzong

6 machines are interconnected through a switch in a peer-to-peer network, then they share an ADSL connection to the Internet through a router/modem. MSN messenger can only receive files but not send them, and voice communication also doesn't work. I heard it's a port mapping problem, but I don't know where to start. Is there any solution? Thanks in advance!