Heads up: Brute force attacks on the rise recently

[Yaakov Nemoy]

2009/10/29 Jim <mickeyboa at sbcglobal.net>:
> On 10/29/2009 08:17 AM, Athmane Madjoudj wrote:
>>
>> On Thu, Oct 29, 2009 at 12:52 PM, jdow<jdow at earthlink.net>  wrote:
>>
>>>
>>> From: "Michael Cronenworth"<mike at cchtml.com>
>>> Sent: Wednesday, 2009/October/28 16:03
>>>
>>>
>>>
>>>>
>>>> It seems in the past month brute force attacks are on the rise. They are
>>>> targeting anyone listening on port 22 and go after root. If you do not
>>>> have a hardened box, you will see thousands upon thousands of
>>>> connections in your logs. Once logged in they will set your system up in
>>>> their botnet.
>>>>
>>>> Google: dt_ssh5
>>>> This little baby will get placed in /tmp and will be running. Looks to
>>>> be a SSH gateway for the attackers for easy access/control.
>>>>
>>>> -Make sure your root password is not a dictionary word.
>>>> -Add iptables rules to limit multiple connections on SSH to 4 within a
>>>> minute.[1] Perhaps this needs to become a Fedora default.
>>>>
>>>
>>> Once within 3 minutes is entirely practical and effective. In the last
>>> two days a pair of dolts kept trying 6621 times and 2185 times after the
>>> door slammed shut in their faces. Their ISPs have been notified.
>>>
>>>
>>>>
>>>> -Update your system.
>>>> -Use SELinux.
>>>>
>>>> Why am I sending this message? Is it SPAM? No. I've seen this hit a
>>>> customer and cause an explosion in their network traffic. The backdoor
>>>> was installed on Sept. 30th and was not detected until recently. Google
>>>> results seem to indicate this past month with higher than normal brute
>>>> force activity.
>>>>
>>>> [1]
>>>> -A INPUT -i eth0 -p tcp -m tcp --dport 22 -m state --state NEW -m recent
>>>> --update --seconds 60 --hitcount 4 --name DEFAULT --rsource -j DROP
>>>> -A INPUT -i eth0 -p tcp -m tcp --dport 22 -m state --state NEW -m recent
>>>> --set --name DEFAULT --rsource
>>>>
>>>
>>> I love those rules and have been spreading them around for quite some
>>> time now. I am glad to see somebody else has either adopted or discovered
>>> the rule trick. It is devastatingly effective. Guessing a password as
>>> simple as "mE3" would take decades of attempts. (Now I want to configure
>>> sshd so that it logs the attempted password along with the attempted user
>>> name.)
>>>
>>> {^_-}
>>>
>>> --
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>>>
>>>
>>
>> You can install fail2ban
>> #yum install fail2ban
>>
>> Links:
>> http://www.fail2ban.org/
>>
>>
>
> Don't install fail2ban you will get twice the amount of "Gold Stars" .
>
> I had fail2ban on a X86_64 box and I was constantly getting selinux Gold
> Stars,
>
> I relabelled fail2ban a number of times to no avail .
>
> I was told it was the way fail2ban was structured wrong, what that means , I
> have no Ideal. But I just uninstalled it.

Have you tried denyhosts yet? We haven't had any SELinux issues with it.

-Yaakov