full-disclosure - Re: targetted SSH bruteforce attacks

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Date: Thu, 17 Jun 2010 21:43:25 -0700
From: BMF <badmotherfsckr@...il.com>
To: Sebastian Rother <sebastian.rother@...erlin.de>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: targetted SSH bruteforce attacks

On Thu, Jun 17, 2010 at 5:31 PM, Sebastian Rother
<sebastian.rother@...erlin.de> wrote:
>  But OpenBSDs "PF" could limit the
> attacks you descripe pretty nicely (and here I have to thanks Henning
> and others for their free time imho, what you made is imho working at
> least).

Here's how it is done on Linux:

iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X

# Block SSH brute force attacks but not our networks like 1.2.3.0/24 etc.
iptables -N SSH_WHITELIST
iptables -A SSH_WHITELIST -s 1.2.3.0/24 -m recent --remove --name SSH -j ACCEPT
iptables -A SSH_WHITELIST -s 4.5.6.0/24 -m recent --remove --name SSH -j ACCEPT

iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent
--set --name SSH
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j SSH_WHITELIST
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent
--update --seconds 60 --hitcount 4 --rttl --name SSH -j LOG
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent
--update --seconds 60 --hitcount 4 --rttl --name SSH -j DROP

BMF

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