Our box is freshly hatched, virgin pixels at the prompt. I favor Ubuntu; if you use another version of linux, your commands may vary. Five minutes to go:
passwd
Change the root password to something long and complex. You won’t need to remember it, just store it somewhere secure - this password will only be needed if you lose the ability to log in over ssh or lose your sudo password.
apt-get update
apt-get upgrade
The above gets us started on the right foot.
apt-get install fail2ban
Fail2ban is a daemon that monitors login attempts to a server and blocks suspicious activity as it occurs. It’s well configured out of the box.
Now, let’s set up your login user. Feel free to name the user something besides ‘deploy’, it’s just a convention we use:
useradd deploy
mkdir /home/deploy
mkdir /home/deploy/.ssh
chmod 700 /home/deploy/.ssh
The days of passwords are over. You’ll enhance security and ease of use in one fell swoop by ditching those passwords and employing public key authentication for your user accounts.
vim /home/deploy/.ssh/authorized_keys
Add the contents of the id_rsa.pub on your local machine and any other public keys that you want to have access to this server to this file.
chmod 400 /home/deploy/.ssh/authorized_keys
chown deploy:deploy /home/deploy -R
Now test your new account logging into your new server with the deploy user (keep the terminal window with the root login open). If you’re successful, switch back to the terminal with the root user active and set a sudo password for your login user:
passwd deploy
Set a complex password - you can either store it somewhere secure or make it something memorable to the team. This is the password you’ll use to sudo.
visudo
Comment all existing user/group grant lines and add:
root ALL=(ALL) ALL
deploy ALL=(ALL) ALL
The above grants sudo access to the deploy user when they enter the proper password.
Configure ssh to prevent password & root logins and lock ssh to particular IPs:
vim /etc/ssh/sshd_config
Add these lines to the file, inserting the ip address from where you will be connecting:
PermitRootLogin no
PasswordAuthentication no
AllowUsers deploy@(your-ip) deploy@(another-ip-if-any)
Now restart ssh:
service ssh restart
No secure server is complete without a firewall. Ubuntu provides ufw, which makes firewall management easy. Run:
ufw allow from {your-ip} to any port 22
ufw allow 80
ufw allow 443
ufw enable
This sets up a basic firewall and configures the server to accept traffic over port 80 and 443. You may wish to add more ports depending on what your server is going to do.
I’ve gotten into the apt-get update/upgrade habit over the years, but with a dozen servers, I found that servers I logged into less frequently weren’t staying as fresh. Especially with load-balanced machines, it’s important that they all stay up to date. Automated security updates scare me somewhat, but not as badly as unpatched security holes.
apt-get install unattended-upgrades
vim /etc/apt/apt.conf.d/10periodic
Update the file to look like this:
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "1";
APT::Periodic::AutocleanInterval "7";
APT::Periodic::Unattended-Upgrade "1";
One more config file to edit:
vim /etc/apt/apt.conf.d/50unattended-upgrades Update the file to look like below. You should probably keep updates disabled and stick with security updates only:
Unattended-Upgrade::Allowed-Origins {
"Ubuntu lucid-security";
// "Ubuntu lucid-updates";
};
Logwatch is a daemon that monitors your logs and emails them to you. This is useful for tracking and detecting intrusion. If someone were to access your server, the logs that are emailed to you will be helpful in determining what happened and when - as the logs on your server might have been compromised.
apt-get install logwatch
vim /etc/cron.daily/00logwatch
add this line:
/usr/sbin/logwatch --output mail --mailto test@gmail.com --detail high
As seen on: https://plusbryan.com/my-first-5-minutes-on-a-server-or-essential-security-for-linux-servers