Verified and Tested 05/9/15

Introduction

This how-to will help you with your initial setup on Ubuntu 15.04 so that you can successfully secure your server while giving you the peace of mind knowing your server is protected. With any server, the primary goal should always be security. Many users are victims of malicious infiltrations on their servers due to the lack of security boundaries established from the beginning. Let us begin on the right path by laying our foundation with security.

What Do You Need?

You need a Ubuntu 15.04 server that is configured with a static IP address. If you do not have a server already, you can visit our industry-leading Cloud Hosting page and spin a new server up in under 30 seconds.

Server Preparation

To get started, login to your Ubuntu 15.04 server via SSH or the VNC Console located here. Atlantic.Net Cloud servers are setup as minimal installations to avoid having unnecessary packages from being installed and never used. If some software packages that you’re used to using aren’t installed by default, feel free to install them as needed.

Let’s make sure that your server is fully up-to-date.

Update the Ubuntu 15.04 Root Password

By default, your Atlantic.Net servers are automatically set with secure passwords. However, we still recommend updating your password after creating your server and every 60-90 days after that to ensure it remains secure. A minimum of 8 characters, including lowercase, uppercase and numbers are recommended to increase the level of security.

Type the following command to activate your request and follow the on-screen instructions to update/confirm your root password:

passwd

Create a new user with sudo privileges

After successfully updating your password, it’s recommended that you create a new user with sudo/root permissions. Since the common admin user for many Linux Operating Systems like Ubuntu 15.04 is “root”, we’re going to make a new admin user that will be used for day-to-day administration tasks. Creating a new user with root permissions will increase the security in the way your server is accessed.  Individuals looking to target your system are going to target the root user because it’s known the be the default admin account. By creating a new user with sudo/root permissions, and disabling the root user, you are increasing security by using a user that isn’t already publicly known.

Type the following command to create your new user replacing “user1”  with your username and confirm.

adduser user1

Fill in the information that applies to the user and confirm the information:

[email protected]:~# adduser user1
Adding user `user1' ...
Adding new group `user1' (1000) ...
Adding new user `user1' (1000) with group `user1' ...
Creating home directory `/home/user1' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for user1
Enter the new value, or press ENTER for the default
 Full Name []: user1
 Room Number []:
 Work Phone []:
 Home Phone []:
 Other []:
Is the information correct? [Y/n] y

Create a password for that user by typing the following command to activate your request and following the on-screen instructions to update/confirm your “user1” password:

passwd user1

Once you have created a new user and created the password for that user, it is time to add the user to the sudo wheel group. In Ubuntu 15.04 once you add them to the sudo wheel group they are automatically assigned sudo/root permissions. Run the following command to add the user to the sudo wheel group.

adduser user1 sudo

Finally when you have created the user with sudo/root permissions,  you can exit your session and log back in with your “user1” to verify the changes that were made. Alternatively, you can run the following command and switch users from root to “user1”  which will then ask you for that users password. It is important to remember that you will then have to use sudo before running any command with the user.

su - user1

Configure SSH Access

In Linux systems, port 22 is the default port for remote connections via SSH. By changing the ssh port, you will increase the security of your server in preventing brute force attacks and unwanted users from reaching your server using the default port. For this tutorial, use Port 5022 as an example.

Open your SSH Configuration file, find the Port line, remove the # and change 22 number to your Custom port Save and exit.

sudo nano /etc/ssh/sshd_config
# What ports, IPs and protocols we listen for
Port 5022

In order for your system to update the new settings from the SSH Configuration file, we must restart the sshd service.

sudo systemctl restart sshd.service

SSH has now been configured to use Port 5022, and if you attempt to login using Port 22, your login will fail. However, do not exit your session as we need to configure the custom port on the firewalls configuration part first, which we will configure in the upcoming steps.

Limit Root Access

Since we’ve created a new user with root permissions and created a custom ssh port, there’s no need keep the actual root user available and vulnerable over SSH on your server. Let us restrict the root users access to be available on the local server and granting permission to the new user over SSH only.

Open the SSH Configuration file, find the PermitRootLogin line, remove the # and change it from yes to no.

sudo nano /etc/ssh/sshd_config
#PermitRootLogin yes
PermitRootLogin no

In order for your system to update the new settings in the SSH Configuration file, we must restart the sshd service.

sudo systemctl restart sshd.service

Note: In making those changes you will now have the root user disabled so you must log into your server with the “user1” that you created. However, do not exit your session, we must configure the custom port on the firewall in the upcoming steps.

Create a Private SSH Key

Private/Public SSH Keys are great additional features that increases security in the method a server is accessed. However, it takes a bit more effort to setup. The question is, Is your server worth the extra security? If you would like to implement the following security features, you can continue with the following steps. Let us proceed and generate the SSH Key.

ssh-keygen

If you want to change the location where the SSH Key will be saved,  you can specify it here. However, the default location where its stored should be OK. Press enter when you are prompted with the following question then enter a passphrase, unless you don’t want one.

Enter file in which to save the key (/home/user1/.ssh/id_rsa):
This is the default page when installing SSH Keys on a Ubuntu 15.04 server

This is the default page when installing SSH Keys on a Ubuntu 15.04 server

Configuring the SSH Key is crucial, we must copy the full key string to a Word/ Notepad Document. The Key can be viewed in the following location with the cat command.

cat ~/.ssh/id_rsa.pub

Copy the SSH key beginning with ssh-rsa and ending with [email protected] into a Word/ Notepad document so we can add it to the config file later on.

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDNcnc3pMOytM7xgwZHUX0Wi/O78hDvLUmQVtKn8Qk1ijBY82jVftKXKRhf8toNkgm9jaZmfapLa7ynzUG4jbFjyy8H+iEs1R8P7eu+e8/fmGwjorbMFuWdoi7h2CldoqKTdMEb/dMNxjNMzBbovl3XtZviQGm4/TMVO1hHxy85JR8zAtNFu7liaP7IonexNrOGhY8CjqRcBsceQLkl1MlX7cWaWAMqd6jQnAvggTLerI9P286AP8Sk4uColj7GKOljj8X6J/2pcjp9v2IvJOqwC/zLwUKZ6qTEV6SrfdbjopoCVvpXkVhmcbHX5Xv1gwynO+vTkpPFwVTjSnAai71L [email protected]

Once the SSH Key is stored safely the directory for the SSH Keys needs limited permissions that only the owner can read, write and execute the file.

sudo chmod 700 .ssh

Within the SSH directory, a file containing the SSH Key must to be added, simply using your editor (in this case NANO) the following location:

nano .ssh/authorized_keys

Paste the SSH Key then save and exit using the nano format.

Finally, we have to limit the permissions of the authorized_keys file that we just created so only owner can read and write.

chmod 600 .ssh/authorized_keys

We could now verify that the key is working by closing the session and typing [email protected] or your servers hostname in your SSH Console. Furthermore, for more information you can click  “here” to see our How To Generate and Use SSH Keys article.

Basic Firewall Rules

By default, your Atlantic.Net’s Ubuntu 15.04 Server is not loaded with a firewall. However, depending on your preference you may install any of the following: firewalld, iptables, etc. In this part I will be using Firewalld which uses the firewall-cmd tool in order to configure its rules. We must first install the Firewall service with the following:

sudo apt-get install firewalld

Next, we’re going to add a rule to allow the custom SSH Port 5022 that was created earlier so it can access the server publicly. At the same time, we’re going to remove the previous default rule allowing SSH access on TCP/22.

sudo firewall-cmd --permanent --add-port=5022/tcp
sudo firewall-cmd --permanent --remove-service=ssh

If you have a web server you may want to allow the following rules so your sites could be accessed over the internet.

sudo firewall-cmd --permanent --add-service=http
sudo firewall-cmd --permanent --add-service=https

You can use this for similar rules related to any systems you want to be publicly accessible. This test server is setup to host a website and email services, so in addition to the updated SSH  and HTTP(S) rules, additional rules for secure POP3, IMAP, and SMTP have been added.

sudo firewall-cmd --permanent --add-service=pop3s
sudo firewall-cmd --permanent --add-service=imaps
sudo firewall-cmd --permanent --add-service=smtp

For Firewalld to accept those settings you must restart the firewall.

sudo firewall-cmd --reload

Your settings will have been saved and you are ready to proceed. To verify all the services/ports that are available run the following:

sudo firewall-cmd --permanent --list-all
This is the default page after configuring the Firewalld rules on Ubuntu 15.04 server

This is the default page after configuring the Firewalld rules on Ubuntu 15.04 server

NTP Time Sync

The NTP (Network Time Protocol) is  used to synchronize the time and date of computers over the network in order to remain accurate and up to date. Let us begin by installing the NTP(If it hasn’t been installed) and configuring the service to synchronize with their servers.

sudo apt-get install ntp

Once the NTP service is installed, we need to make sure that the service is ON.

sudo /etc/init.d/ntp start

Add Swap File

A Swap file is simply a small amount of space created on a servers hard drive to simulate Ram. In the event that the server is running low on memory it will look at the hard drive and ease the load tricking the system to think it has more memory. We will set up the swap file on the hard drive to increase the performance of the server just a little bit more.

Begin by checking your resources to make sure we can add the file. When you run the following command, you will see the percentage space on your Hard drive that is currently being used.

df -h

When creating a Swap file usually you want to add half of your existing RAM up to 4GB(If you have 1GB of actual Ram then you add a 512MB file). In this part I will be adding a 512MB swap file to the drive. The way that this is calculated is by 1024 x 512MB = 524288 block size.

sudo dd if=/dev/zero of=/swapfile bs=1024 count=524288

Now that we have added a swap file, a Swap file area needs to be created in order to proceed.

sudo mkswap /swapfile

With the Swap file created and the Swap file, area added we can go ahead and add permissions to the file so that only the owner can read and write.

sudo chown root:root /swapfile
sudo chmod 600 /swapfile

Now that the swap file has the appropriate permissions we can go ahead and activate the it.

sudo swapon /swapfile

You can verify your newly added Swap file with the following.

sudo swapon -s

In order to make the Swap file always active even after a reboot, we must configure it accordingly.

sudo nano /etc/fstab

Paste the following command at the bottom of the file save your work and exit.

/swapfile              swap   swap     defaults     0 0

Finally, verify if your swapfile is activated by typing the following command:

free -m
This is the default page after creating a Swap File on a Ubuntu 15.04 Server

This is the default page after creating a Swap File on a Ubuntu 15.04 Server

What Next?

With that, you now have a server with a strong security foundation which will give you the peace of mind knowing that your server is protected. You may now proceed to build your platform according to your needs. Thank you for following along and feel free to check back with us for further updates.

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