Hello Skunkers

I have a Linux Box that is on the internet.I have several times noticed
that when i look at my log files in /var/log/secure  i notice alot of
possible break in attempts eg

32 proxicious sshd[32036]: pam_unix(sshd:auth): authentication failure;
logname= uid=0 euid=0 tty=ssh ruser= rhost=cl67-179-182-213.cl.metrocom.ru
 user=root
Jan 25 19:02:34 proxicious sshd[32036]: Failed password for root from
213.182.179.67 port 47122 ssh2
Jan 25 19:02:34 proxicious sshd[32037]: Received disconnect from
213.182.179.67: 11: Bye Bye
Jan 25 19:02:36 proxicious sshd[32038]: pam_unix(sshd:auth):
authentication failure; logname= uid=0

There are so many ip addresses trying to enter this box.I have been
blocking the IP addresses using

iptables -A INPUT -s a.b.c.d -j DROP  from the box.

My question is,if there are very many IP's trying;is there a simpler
method of doing this or do i have to do it one by one.(really frustrating)
PS I have not enabled SELinux becoz sometimes it becomes a hindrance alot.