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Re: SSH server under attack...
From: xyberpix <xyberpix () xyberpix com>
Date: Sun, 29 Jan 2006 13:37:25 +0000

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Blackhole the attacking IP on your firewall, as you know what the IP is, or add a route on your router to drop it.

xyberpix

Blog: http://blogs.securiteam.com



On 23 Jan 2006, at 21:40, Dave wrote:

My SSH server has been under DoS and I cant stop it!!!

I changed the port of the SSH server from 22 to 2222. This isnt going to really do much but it would stop some automated script that attacks port 22. OK...within a few hours the server was being attacked again on port
2222. This is an *active* attacker, active in that he is actively
monitoring what he is doing. The router/firewall logs dont show any
dropped packets sent to port 22 so he changed the port of the attack
script. Now, the new machine to attack me is 200.55.192.29. This belongs
to a company in south america called 'Springs South America Textiles
Ltda.'. I scanned the machine and found that it is hosting a webserver
(Apache/2.0.52 (Fedora) Server at www.springs.cl) among other services. The last machine the attacker used to brute_force me was also an apache server (rh linux). So this attacker is cracking various webservers (most
likely) or some other service on these boxes in order to use these
machines as an attack platform. Now, yes, i notified the admin of this
company etc..but think of this. If this admin is going to put an
*unused* and unprotected server on the net then what kind of admin is
he? Will he even care about my email? Who knows! Calling the authorities
is not going to work 'cause frankly I am a nobody...who cares if my
servers are under attack! No one is going to waste resource (money) in
trying to find this guy, so really its up to me. So what do we know
about this guy? At first the info seems conflicting: He has the ability to crack a number of random servers and use them at his disposal but he
is running the same stupid attack over and over...why? First off, the
attack is a brute force attack. He is trying to guess a username
password combo in order to be able to log into my server and get shell
access...but maybe not. Like I said..he is no dummy. So what is he
doing? I think DoS (denial of service) , the brute force tool is just
the means to an end. He isnt trying to break in by doing this. Maybe he coudnt break in to my server so he is resorting to the next trick up his
sleeve. By having all these machines attempting to log into my server
over and over he might be trying to use up my bandwidth in effect
causing a DoS to anyone! OR...In closely looking at the logs you will
notice something *unusual*:

Failed password for invalid user admin from ::ffff:200.55.192.29 port
34182 ssh2
Invalid user admin from ::ffff:200.55.192.29
Failed password for invalid user admin from ::ffff:200.55.192.29 port
34679 ssh2
Invalid user admin from ::ffff:200.55.192.29
Failed password for invalid user admin from ::ffff:200.55.192.29 port
34752 ssh2
Invalid user administrator from ::ffff:200.55.192.29
Failed password for invalid user administrator from ::ffff: 200.55.192.29
port 35253 ssh2
Invalid user administrator from ::ffff:200.55.192.29
Failed password for invalid user administrator from ::ffff: 200.55.192.29
port 35735 ssh2
Invalid user administrator from ::ffff:200.55.192.29
Failed password for invalid user administrator from ::ffff: 200.55.192.29
port 36237 ssh2
Invalid user tads from ::ffff:200.55.192.29
Failed password for invalid user tads from ::ffff:200.55.192.29 port
36703 ssh2
Invalid user tads from ::ffff:200.55.192.29
Failed password for invalid user tads from ::ffff:200.55.192.29 port
36813 ssh2
Invalid user tads from ::ffff:200.55.192.29
Failed password for invalid user tads from ::ffff:200.55.192.29 port
37332 ssh2
Invalid user tip from ::ffff:200.55.192.29
Failed password for invalid user tip from ::ffff:200.55.192.29 port
37820 ssh2
Invalid user tip from ::ffff:200.55.192.29
Failed password for invalid user tip from ::ffff:200.55.192.29 port
38267 ssh2
Invalid user tip from ::ffff:200.55.192.29
Failed password for invalid user tip from ::ffff:200.55.192.29 port
38757 ssh2
Invalid user myra from ::ffff:200.55.192.29
Failed password for invalid user myra from ::ffff:200.55.192.29 port
38844 ssh2
Invalid user myra from ::ffff:200.55.192.29
Failed password for invalid user myra from ::ffff:200.55.192.29 port
39333 ssh2
Invalid user myra from ::ffff:200.55.192.29
Failed password for invalid user myra from ::ffff:200.55.192.29 port
39812 ssh2
Invalid user jack from ::ffff:200.55.192.29
Failed password for invalid user jack from ::ffff:200.55.192.29 port
40312 ssh2
Invalid user jack from ::ffff:200.55.192.29
Failed password for invalid user jack from ::ffff:200.55.192.29 port
40787 ssh2
Invalid user jack from ::ffff:200.55.192.29
Failed password for invalid user jack from ::ffff:200.55.192.29 port
40893 ssh2
Invalid user sya from ::ffff:200.55.192.29


Each user name was tried three times. What does this
mean...I dont know but right off hand I would guess that he is trying to lock out legit user accounts. You see some servers will disallow a user to log in if they entered three wrong passwords. This, strangely enough,
is used to help stop brute forcing!!! Anyway, The attacker has put
together a list of *potential* user names that *might* be found on my
server and is attempting to lock them out...in effect creating a DoS to
any users whose names appear on this list.

He also knew right away when I changed the sshd port number and wasted
no time in getting another machine to attack me via this port!

Authorities arent going to help...Servers admin prob doesnt care plus
the attacker most likely has access to any number of servers so writing
the abuse lines could be a daily chore just to keep up...any
recommendations?

Any help / comments / flames appreciated

take it easy...
dave

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EARN A MASTER OF SCIENCE IN INFORMATION ASSURANCE - ONLINE
The Norwich University program offers unparalleled Infosec management education and the case study affords you unmatched consulting experience. Tailor your education to your own professional goals with degree customizations including Emergency Management, Business Continuity Planning, Computer Emergency Response Teams, and Digital Investigations.
http://www.msia.norwich.edu/secfocus
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