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Managing SSH Settings

In this lab, we will look at how to manage SSH settings on a Linux host. We will change the default listening port of SSH on a Linux host. Then, we'll configure SSH restrictions on the host to only permit SSH from a specific subnet.

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Path Info

Clock icon Beginner
Clock icon 30m
Clock icon Apr 15, 2019

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Table of Contents

  1. Challenge

    Change the default SSH port 22 to port 22000.

    1. To change the default port of 22 to 22000 for SSH, we'll need to edit the sshd_config file with the following command:
    sudo nano /etc/ssh/sshd_config
    1. Then, we'll need to edit one of the lines:
    Uncomment "#Port 22" and replace 22 with 22000
    1. Now, we'll need to restart the SSH service:
    sudo service sshd restart
  2. Challenge

    Restrict SSH by Source IP using TCP Wrappers.

    1. We will need to edit the hosts.allow and hosts.deny files used by TCP Wrappers. Let's start with the hosts.deny file:

      sudo nano /etc/hosts.deny

      Add the line:

      sshd : ALL

      Then, save and exit the file.

    2. Now we need to edit the hosts.allow file:

      sudo nano /etc/hosts.allow  

      Add the following line:

      sshd :  

      Save and close the file.

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