Configuring a Service with Host Based Security Restrictions

1 hour
  • 3 Learning Objectives

About this Hands-on Lab

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.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

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:

sshd: 10.0.1.101
Log All Connection Denials

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

sshd: 10.0.1.101  : spawn /bin/echo $(/bin/date) %a access denied >> /var/log/sshd  :deny
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

Additional Resources

Once this activity is started, you will be provisioned TWO CentOS 7 systems, along with user credentials and connectivity information.

Once connected to the SERVER instance as indicated on your screen, open you Activity Guide for instructions on how to complete this lab.

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