Three ways to close Linux system ports

#How to close a port under Linux system, this article mainly shares with you, I hope it can help you.

1. Close the port by killing the process

Each port has a daemon process, just kill the daemon process

Every Each port is occupied by a process.

The first step is to use the following command

netstat -anp |grep port

Find out the process occupying this port,

Second step, use the following command

kill -9 PID

Just kill it

2. Open the service by opening and closing the service /Close port

Because each port has a corresponding service, so to close the port, you only need to close the corresponding service.

Services that are automatically started at boot in Linux are generally stored in two places:

Services under the /etc/init.d/ folder:
The services in this folder can be started or shut down by running the corresponding SCRIPT.
For example: start the sendmail service: ./sendmail start (opens the TCP 25 port)
Close the sendmail service: ./sendmail stop (closes the TCP 25 port)

View the current status of the sendmail service Status: ./sendmail? status (check whether the service is running)

Services under the /etc/xinetd.d/ folder:
The services under this folder need to be changed Service configuration file and restart xinetd.

For example: To start the auth service, open the /etc/xinetd.d/auth configuration file, change "disable=no", save and exit.

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

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

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

3. Restrict ports through the firewall

The method introduced below can be used under Linux commands, which is very simple .
Open the port as:

iptables -A INPUT -p $port -j ACCEPT

Just change ACCEPT to DROP, that is:

iptables -A INPUT -p $port -j DROP
where $port is the port number, the specific usage of iptables can be.

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