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Old 07-31-2007, 02:26 AM   #1
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Registered: Nov 2004
Posts: 28

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blocking false ssh users with ossec


I have two questions.

My ssh port is 22. But I'm getting these emails from ossec which indicate ssh connection to funky ports

Jul 30 09:42:40 ns1 sshd[3937]: Invalid user adauto from
Jul 30 09:42:40 ns1 sshd[3936]: Invalid user frida from
Jul 30 09:42:11 ns1 sshd[3932]: Failed password for invalid user fuad from port 56565 ssh2
Jul 30 09:42:08 ns1 sshd[3932]: Invalid user fuad from
Jul 30 09:41:59 ns1 sshd[3930]: Failed password for invalid user frida from port 56494 ssh2
Jul 30 09:41:57 ns1 sshd[3930]: Invalid user frida from
Jul 30 09:41:54 ns1 sshd[3928]: Failed password for invalid user frida from port 56406 ssh2
I have only a couple of handful ports open by APF and those listed are not. So my first question is how could this be?

My second question is, how can I add the IPs of these attackers to host.deny with ossec automatically?

Last edited by txm123; 07-31-2007 at 02:28 AM.
Old 07-31-2007, 03:20 AM   #2
Registered: Oct 2004
Distribution: Slackware
Posts: 376

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For your first question: those ports are where those users are connecting FROM, not TO. Your ssh daemon only listens on port 22, but ssh clients may connect from any port. This is safe and expected - it's just how TCP works.

Adding hosts to hosts.deny is pretty simple, but I don't know anything about ossec or how to get it to do it for you.
Old 07-31-2007, 02:51 PM   #3
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Registered: Jun 2003
Location: California
Distribution: Slackware
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As a (psuedo-random) aside, if you change your incoming SSH port, you'll have fewer login attacks by order of magnitudes. I bumped mine from 22 to 28 (for example) and instead of registering ~500 a day, I get 1 a week.


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