Method 1: Using Fail2ban Client
sudo fail2ban-client set sshd banip 192.168.1.100Method 2: Manual iptables Ban
sudo iptables -A INPUT -s 203.0.113.45 -j DROPMethod 3: Using UFW
sudo ufw deny from 203.0.113.45Permanent bans should be used carefully. Consider temporary bans for dynamic IPs.