How to limit access to SSH to one (or more) IPs

IMPORTANT NOTE: This may work for you well, but keep in mind that these methods are not universal. These are examples of basic use; we highly recommend you to check the documentation for a better understanding of how to set up these utilities for your needs.

IPTables (Universal)

Firstly, let’s allow access to your IP:

iptables -A INPUT --source Y -p tcp --dport 22 -j ACCEPT

NOTE: 22 is a standard port; if you are using another port, you need to change the —dport parameter to your port.

Then we need to block access for other IPs:

iptables -A INPUT -p tcp --dport 22 -j DROP

For more information, visit - https://linux.die.net/man/8/iptables

Firewalld (CentOS/Alma Linux)

Keep in mind that Firewalld is usually a built-in utility, so in some cases, installation is not needed.

Upgrade your package and install Firewalld using the next command:

yum upgrade --refresh -y && yum -y install firewalld

Enable and start Firewalld:

systemctl enable firewalld && systemctl start firewalld && systemctl status firewalld

Add a new zone and set it up:

firewall-cmd --permanent --new-zone=ssh-limited
firewall-cmd --permanent --zone=ssh-limited --add-source=my_IPAddress

Add SSH service to the new zone:

firewall-cmd --permanent --zone=ssh-limited --add-service=ssh

Remove SSH from the public zone:

firewall-cmd --permanent --remove-service=ssh

Apply changes:

firewall-cmd --reload

To see the list of active zones, type:

firewall-cmd --get-active-zones

For more information, visit - https://firewalld.org/documentation

UFW (Ubuntu/Debian)

UFW is an easy-to-use utility, usually built-in, but not always.

Upgrade your package and install UFW using the next command:

apt update -y && apt install -y ufw

Allow access for your address:

ufw limit from My_IPAddress to any app OpenSSH

Remove less-restrictive SSH-related rules:

ufw delete allow 22/tcp
ufw delete allow OpenSSH
ufw delete limit OpenSSH

Enable UFW:

ufw --force enable

To see status:

ufw status

For more information about UFW, visit - https://ubuntu.com/server/docs/security-firewall