(When surfing the Internet, we often see the word "port" and often use the port number. For example, "21" is added after the FTP address, and 21 represents the port number. So what does the port mean? How to detect the port number? Does a port become the door to malicious network attacks? How should we face all kinds of ports? The following will introduce the content of this aspect for our reference. Port 21: Port 21 is mainly used for FTP (FileTransferProtocol, file transfer protocol) services. Port description: Port 21 is mainly used for FTP (FileTransferProtocol, file transfer protocol) service. FTP service is mainly for uploading and downloading files between two computers. One computer is used as an FTP client, and the other computer is used as FTP. The server can log in to the FTP server using two methods: anonymous login and authorized user name and password login. In Windows, FTP connection and management can be provided through Internet Information Services (IIS), and FTP server software can also be installed independently to realize FTP function, such as the common FTPServ-U. Operation suggestion: Because some FTP servers can log in anonymously, they are often used by hackers. In addition, port 21 is also used by some Trojans, such as BladeRunner, FTPTrojan, DolyTrojan, WebEx, etc. If you do not set up an FTP server, it is recommended to close port 21. Port 23: Port 23 is mainly used for Telnet (remote login) services, which are widely used login and emulation programs on the Internet.)
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