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From: Mel <fbsd.questions@rachie.is-a-geek.net>
To: freebsd-questions@freebsd.org
Date: Thu, 18 Sep 2008 01:49:16 +0200
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Cc: "Marc G. Fournier" <scrappy@hub.org>
Subject: Re: Auto blacklist ssh connections ...
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On Thursday 18 September 2008 01:15:45 Marc G. Fournier wrote:
> Does anyone know of a utility that I can use with sshd to auto-block by IP
> if there are more then N failed attempts in a row?

# crontab -l
@reboot /usr/sbin/daemon -p /var/run/grok-ssh.pid /usr/local/bin/grok -f /etc/pf/grok-ssh.conf

# grep -- -0F /usr/local/bin/grok
my $TAIL = "/usr/bin/tail -0F";

^^^^ so that newsyslog doesn't interfere.

$ cat /etc/pf/grok-ssh.conf
file "/var/log/auth.log" {
        type "ssh-illegal-user" {
                match = "Invalid user %USERNAME% from %IP%";
                threshold = 5;   # 5 hits ...
                key = "%IP%";    # from a single ip ...
                interval = 60;   # in 1 minutes
                reaction = "/root/bin/pfscanners %IP%"; # permanent
        };

        type "ssh-scan-possible" {
                match = "Did not receive identification string from %IP%";
                threshold = 3;
                interval = 60;
                reaction = "/sbin/pfctl -t scanners -Tadd %IP%"; #temporary
        };
};

$ cat /root/bin/pfscanners
#!/bin/sh

while( test ! -z "$1" ); do
        /sbin/pfctl -t scanners -Tadd $1
        echo $1 >> /etc/pf/scanners.table
        shift
done

$ grep scanners /etc/pf.conf
table <scanners> persist file "/etc/pf/scanners.table"
block in log on $ext_if from <scanners>

-- 
Mel

Problem with today's modular software: they start with the modules
    and never get to the software part.