Lab
A Cloud Guru

Locking Down Remote Access to Linux

In this lab, we will look at how to lock down remote access to a Linux host. We will accomplish this by restricting all remote logins for the `root` account as well as restricting SSH access based on account names.

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Path Info

Level

Beginner

Duration

30m

Published

Apr 15, 2019

Challenge

Prevent remote logins from using the `root` account.
1. In order to prevent remote logins from using the root account, we'll need to edit the /etc/passwd file. Run the following command:
```
sudo vipw 
```
  - select #2 for nano (easiest)
2. Next, edit the line that starts with root and replace /bin/bash with /sbin/nologin.
3. Save and exit the /etc/passwd file.
Challenge

Permit only the `cloud_user` account to connect to the host via SSH.
1. In order to filter SSH access and only permit the cloud_user account to access the host via SSH, we'll need to edit the sshd_config file with the following command:
```
sudo nano /etc/ssh/sshd_config
```
2. Add the following line to the file just under the second line of the file:
```
AllowUsers cloud_user
```
  Note: You can also restrict user access by source hostname, IP address, or subnet, like:
```
AllowUsers [email protected]/24
AllowUsers [email protected]
AllowUsers [email protected]
```
3. Now, restart the ssh service with the following command:
```
sudo service ssh restart
```

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!

What's a lab?

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.