Lab
A Cloud Guru

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

Level

Intermediate

Duration

1h 0m

Published

Nov 12, 2018

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:
```
sshd: 10.0.1.101
```
Challenge

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
```
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

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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