Iptables rules sometimes are reset automatically
Solution 1:
sudo iptables -A INPUT -s 89.111.3.48 -j DROP
If you just run the above command, it just loads that rule into the kernel, not really changing the iptables file. This would be lost on a reboot or a restart of iptables.
service iptables save
would save the rules to /etc/sysconfig/iptables and the change would survive a reboot.