To block an IP on your Linux server you need to use iptables tools and netfilter firewall. First you need to log into shell as root user. To block an IP address you need to type the iptables command as follows:
# iptables -A INPUT -s IP-ADDRESS -j DROP
Replace IP-ADDRESS with your actual IP address. For example, if you wish to block an ip address 209.175.453.23 for whatever reason then type the command as follows:# iptables -A INPUT -s 209.175.453.23 -j DROP
If you have IP tables firewall script, add the above rule to your script.If you just want to block access to one port from an ip 209.175.453.23 to port 22 then type command:# iptables -A INPUT -s 209.175.453.23 -p tcp --destination-port 22 -j DROP
CentOS / RHEL / Fedora Block An IP And Save It To Config File
Type the following two command:
# iptables -A INPUT -s 209.175.453.23 -j DROP
# service iptables save
HOW TO UNBLOCK AN IP ADDRESS ON A LINUX SERVER
Use the following syntax (the -d options deletes the rule from table):
# iptables -D INPUT -s 209.175.453.23 -j DROP
# service iptables save
