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Configuring a Service with Host Based Security Restrictions

Outside of using a Firewall, it is important to understsand that there are other methods of configuring a service with host based security restrictions. Using the hosts.allow and deny files, we will explore how TCP Wrappers works to secure our systems.

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Path Info

Clock icon Intermediate
Clock icon 1h 0m
Clock icon Nov 12, 2018

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Table of Contents

  1. Challenge

    Keep Client System from Connecting Over SSH

    This is accomplished using the /etc/hosts.deny file (remember, if we try to allow specific locations, whatever is in /etc/hosts.allow will be applied first). You can accomplish this by making the following addition to the /etc/hosts.deny file:

  2. Challenge

    Log All Connection Denials

    Within the /etc/hosts.deny file, you will need to add the following in order to log connections:

    sshd: \ : spawn /bin/echo $(/bin/date) %a access denied >> /var/log/sshd \ :deny
  3. Challenge

    Reload the SSH Service and Verify

    You can reload (without disconnecting yourself) the SSH configuration via:

    systemctl reload sshd

    Then verify by trying to connect to the SERVER from the CLIENT system over SSH and viewing the denial message in /var/log/sshd.log

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