Re: SSH Brute force attacks

["Taylor, Grant" <gtaylor@riverviewtech.net>]

> One one of my hosted boxes, my logwatch scripts continuously pipe out my 
> ssh and auth log of unsuccessful dictionary attacks
> 
> I came across this link : http://blog.andrew.net.au/2005/02/17/

Not a bad idea, but I think there is a little bit of room for growth.

# Let's jump to the SSH_Brute_Force chain if this is a new connection that is not from my IP address.
# This will prevent processing these rules for non SSH traffic.
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j SSH_Brute_Force
# Let's white list some IP addresses.
iptables -A SSH_Brute_Force -s $My_IP_Address -j RETURN
iptables -A SSH_Brute_Force -s $My_Friends_IP_Address -j RETURN
iptables -A SSH_Brute_Force -s $Any_other_IP_that_I_want_to_white list -j RETURN
# If there have not been 4 NEW connection attempts from this source IP address in the last 60 seconds let's return to the INPUT chain.
iptables -A SSH_Brute_Force -m recent --name SSH ! --rcheck --seconds 60 -m recent --hitcount 4 --set --name SSH -j RETURN
# Well, the NEW connection has been seen so let's update the SSH recent list.
iptables -A SSH_Brute_Force -m recent --name SSH --update
# I like to log on a line by it's self so I don't have to remember to do it on my last line prior to the end of my script.
iptables -A SSH_Brute_Force -j LOG --log-prefix "SSH Brute Force Attempt:  "
# Let's send the person that is trying to SSH in to us to the TARPIT target and make them think twice before they try again.
# TARPIT will force the site that is SSHing in to us to timeout the connection.  Sure stick you hand in my port, I'll grab hold of it and not let go,
# you will have to chew your arm off and grow a new one and try again.  I'll hold your new arm again and again and again and...  This should slow you down.
iptables -A SSH_Brute_Force -j TARPIT
# I can be a mean vindictive SoB (Sweet Old Buzzard.  NOT!)

I tried putting in comments to explain the logic of what is going on, if you have any questions please let me know.



Grant. . . .