3 ways to turn off Linux system ports

Here's a summary of three ways to turn off Linux system ports

1. Close the port by killing the process

Each port has a daemon, kill the daemon.

Each port is a process occupied,

The first step, use the following command

NETSTAT-ANP |grep Port

Find the process that occupies this port.

The second step, use the following command

Kill PID

Just kill it.

2. Turn on/off the port by turning off the service

Because each port has a corresponding service, it is possible to close the port as long as the corresponding service is turned off.

Linux boot auto-start services are generally stored in two places:

services under the/etc/init.d/folder:
The services under this folder can be started or closed by running the appropriate script.
Example: Start the SendMail service:./sendmail Start (TCP 25 port is turned on)
Close SendMail service:./sendmail Stop (TCP 25 port off)

View the current status of the SendMail service:./sendmail? Status (see if the service is running)

services under the/etc/xinetd.d/folder:
The service under this folder needs to be changed by changing the service configuration file and restarting xinetd.

For example: To start the Auth service, open the/etc/xinetd.d/auth profile, change the "Disable=no", and save the exit.

Run/etc/rc.d/init.d/xinetd restart

To stop the Auth service, open the/etc/xinetd.d/auth configuration file, change the "Disable=yes", and save the exit.

Run/etc/rc.d/init.d/xinetd restart

3. Restricting ports through firewalls

The methods described below are used under Linux commands and are easy to use.
Opening ports are:

Iptables-a input-p $port-j ACCEPT

Switch the Accept to drop, i.e.:

Iptables-a input-p $port-j DROP
Where $port is the port number

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3 ways to turn off Linux system ports