Monday, November 24, 2008

Distributed SSH Brute Force Attempts, part 2

OK, so I'm still curious about the distributed SSH brute force attempts I've been seeing.

I wanted to check all my logs and not just the most recent logfile. Looking at my /var/log directory:

-su-2.05b# ls | grep auth
auth.log
auth.log.0.bz2
auth.log.1.bz2
auth.log.2.bz2
auth.log.3.bz2
auth.log.4.bz2
auth.log.5.bz2
auth.log.6.bz2
auth.log.7.bz2


I tailed the auth.log file and grabbed a random IP:

Nov 24 21:53:59 delly sshd[75490]: Invalid user bryan from 170.56.255.20
Nov 24 21:54:00 delly sshd[75490]: error: PAM: authentication error for illegal user bryan from 170.56.255.20
Nov 24 21:54:00 delly sshd[75490]: Failed keyboard-interactive/pam for invalid user bryan from 170.56.255.20 port 43229 ssh2


I then wanted to check all the auth.log.* files, but was curious as to how I could check compressed files. I found that there's a command called bzgrep that allows one to grep compressed files, so I used the following command and came up with quite a few hits for the referenced IP over seven (7) log files:

-su-2.05b# bzgrep '170.56.255.20' auth.log.*


The results show 2-3 instances of log entries per login attempt, so I wanted to isolate each instance without having to use arcane sed and sort commands, so I used the following:


-su-2.05b# bzgrep '170.56.255.20' auth.log.* | grep 'Invalid user' | wc -l
19


So, this particular IP generated 19 log entries between 22 and 24 Nov.

That's not particularly good. I'd love to create a script that would break down all of these IPs' unique login attempts (and possibly block them). Sounds like a project, no? :)

I've a bit of time, so I did the following (non-scripted). I cat'd the auth.log file and collected a screens-worth of data:

-su-2.05b# cat auth.log | less
Nov 24 15:00:00 delly newsyslog[74001]: logfile turned over due to size>100K
Nov 24 15:00:49 delly sshd[74014]: Invalid user brand from 218.80.215.198
Nov 24 15:00:50 delly sshd[74014]: error: PAM: authentication error for illegal user brand from 218.80.215.198
Nov 24 15:00:50 delly sshd[74014]: Failed keyboard-interactive/pam for invalid user brand from 218.80.215.198 port 19051 ssh2
Nov 24 15:02:25 delly sshd[74017]: Invalid user brandee from 83.19.224.11
Nov 24 15:02:26 delly sshd[74017]: error: PAM: authentication error for illegal user brandee from dum11.internetdsl.tpnet.pl
Nov 24 15:02:26 delly sshd[74017]: Failed keyboard-interactive/pam for invalid user brandee from 83.19.224.11 port 50163 ssh2
Nov 24 15:03:48 delly sshd[74020]: Invalid user brandee from 194.224.118.61
Nov 24 15:03:48 delly sshd[74020]: error: PAM: authentication error for illegal user brandee from 194.224.118.61
Nov 24 15:03:48 delly sshd[74020]: Failed keyboard-interactive/pam for invalid user brandee from 194.224.118.61 port 6345 ssh2
Nov 24 15:05:21 delly sshd[74026]: Invalid user brandee from 90.176.233.222
Nov 24 15:05:22 delly sshd[74026]: error: PAM: authentication error for illegal user brandee from 222.233.broadband9.iol.cz
Nov 24 15:05:22 delly sshd[74026]: Failed keyboard-interactive/pam for invalid user brandee from 90.176.233.222 port 46108 ssh2
Nov 24 15:06:42 delly sshd[74029]: Invalid user branden from 125.77.106.246
Nov 24 15:06:42 delly sshd[74029]: error: PAM: authentication error for illegal user branden from 125.77.106.246
Nov 24 15:06:42 delly sshd[74029]: Failed keyboard-interactive/pam for invalid user branden from 125.77.106.246 port 46495 ssh2
Nov 24 15:10:59 delly sshd[74035]: Invalid user brandi from 122.224.128.222
Nov 24 15:10:59 delly sshd[74035]: error: PAM: authentication error for illegal user brandi from 122.224.128.222
Nov 24 15:10:59 delly sshd[74035]: Failed keyboard-interactive/pam for invalid user brandi from 122.224.128.222 port 42253 ssh2
Nov 24 15:12:27 delly sshd[74051]: Invalid user brandi from 59.125.200.51
Nov 24 15:12:28 delly sshd[74051]: error: PAM: authentication error for illegal user brandi from 3w.upcc.com.tw
Nov 24 15:12:28 delly sshd[74051]: Failed keyboard-interactive/pam for invalid user brandi from 59.125.200.51 port 14046 ssh2
Nov 24 15:15:23 delly sshd[74057]: Invalid user brandice from 62.112.222.88
Nov 24 15:15:24 delly sshd[74057]: error: PAM: authentication error for illegal user brandice from 3e70de58.adsl.enternet.hu
Nov 24 15:15:24 delly sshd[74057]: Failed keyboard-interactive/pam for invalid user brandice from 62.112.222.88 port 42127 ssh2
Nov 24 15:16:49 delly sshd[74060]: Invalid user brandice from 218.80.215.198
Nov 24 15:16:50 delly sshd[74060]: error: PAM: authentication error for illegal user brandice from 218.80.215.198
Nov 24 15:16:50 delly sshd[74060]: Failed keyboard-interactive/pam for invalid user brandice from 218.80.215.198 port 57929 ssh2
Nov 24 15:18:11 delly sshd[74063]: Invalid user brandice from 65.203.231.41
Nov 24 15:18:11 delly sshd[74063]: error: PAM: authentication error for illegal user brandice from 65.203.231.41
Nov 24 15:18:11 delly sshd[74063]: Failed keyboard-interactive/pam for invalid user brandice from 65.203.231.41 port 38395 ssh2
Nov 24 15:19:43 delly sshd[74066]: Invalid user brandie from 123.14.10.64
Nov 24 15:19:44 delly sshd[74066]: error: PAM: authentication error for illegal user brandie from 123.14.10.64
Nov 24 15:19:44 delly sshd[74066]: Failed keyboard-interactive/pam for invalid user brandie from 123.14.10.64 port 4925 ssh2
Nov 24 15:21:07 delly sshd[74072]: Invalid user brandie from 200.170.141.134
Nov 24 15:21:07 delly sshd[74072]: error: PAM: authentication error for illegal user brandie from 200-170-141-134.static.ctbctelecom.com.br
Nov 24 15:21:07 delly sshd[74072]: Failed keyboard-interactive/pam for invalid user brandie from 200.170.141.134 port 39979 ssh2
Nov 24 15:22:44 delly sshd[74088]: Invalid user brandie from 80.51.31.84
Nov 24 15:22:44 delly sshd[74088]: error: PAM: authentication error for illegal user brandie from 80.51.31.84
Nov 24 15:22:44 delly sshd[74088]: Failed keyboard-interactive/pam for invalid user brandie from 80.51.31.84 port 39453 ssh2
Nov 24 15:24:02 delly sshd[74091]: Invalid user brandon from 200.157.176.13
Nov 24 15:24:03 delly sshd[74091]: error: PAM: authentication error for illegal user brandon from 200.157.176.13
Nov 24 15:24:03 delly sshd[74091]: Failed keyboard-interactive/pam for invalid user brandon from 200.157.176.13 port 54638 ssh2

I then checked every IP for unique log entries within all of my ssh logs:

-su-2.05b# bzgrep '218.80.215.198' auth.log.* | grep 'Invalid user' | wc -l
6

-su-2.05b# bzgrep '218.80.215.198' auth.log.* | grep 'Invalid user'
auth.log.0.bz2:Nov 24 10:55:25 delly sshd[73084]: Invalid user bjorn from 218.80.215.198
auth.log.1.bz2:Nov 23 23:22:28 delly sshd[70023]: Invalid user bahari from 218.80.215.198
auth.log.3.bz2:Nov 23 11:18:54 delly sshd[66908]: Invalid user archibald from 218.80.215.198
auth.log.4.bz2:Nov 23 04:11:52 delly sshd[65051]: Invalid user amy from 218.80.215.198
auth.log.5.bz2:Nov 22 23:20:53 delly sshd[63465]: Invalid user alize from 218.80.215.198
auth.log.7.bz2:Nov 22 01:07:10 delly sshd[57652]: Invalid user claire from 218.80.215.198

-su-2.05b# bzgrep '83.19.224.11' auth.log.* | grep 'Invalid user' | wc -l
8
-su-2.05b# bzgrep '194.224.118.61' auth.log.* | grep 'Invalid user' | wc -l
11
-su-2.05b# bzgrep '90.176.233.222' auth.log.* | grep 'Invalid user' | wc -l
0
-su-2.05b# bzgrep '125.77.106.246' auth.log.* | grep 'Invalid user' | wc -l
9
-su-2.05b# bzgrep '122.224.128.222' auth.log.* | grep 'Invalid user' | wc -l
8
-su-2.05b# bzgrep '59.125.200.51' auth.log.* | grep 'Invalid user' | wc -l
5
-su-2.05b# bzgrep '62.112.222.88' auth.log.* | grep 'Invalid user' | wc -l
10
-su-2.05b# bzgrep '218.80.215.198' auth.log.* | grep 'Invalid user' | wc -l
6
-su-2.05b# bzgrep '65.203.231.41' auth.log.* | grep 'Invalid user' | wc -l
15

-su-2.05b# bzgrep '65.203.231.41' auth.log.* | grep 'Invalid user'
auth.log.0.bz2:Nov 24 14:56:28 delly sshd[73982]: Invalid user bran from 65.203.231.41
auth.log.1.bz2:Nov 23 22:32:01 delly sshd[69793]: Invalid user azra from 65.203.231.41
auth.log.1.bz2:Nov 24 02:04:43 delly sshd[70680]: Invalid user bartholemew from 65.203.231.41
auth.log.1.bz2:Nov 24 04:07:45 delly sshd[71474]: Invalid user beck from 65.203.231.41
auth.log.2.bz2:Nov 23 19:02:03 delly sshd[68866]: Invalid user aurora from 65.203.231.41
auth.log.2.bz2:Nov 23 20:16:18 delly sshd[69213]: Invalid user avi from 65.203.231.41
auth.log.3.bz2:Nov 23 10:08:33 delly sshd[66592]: Invalid user april from 65.203.231.41
auth.log.3.bz2:Nov 23 10:24:43 delly sshd[66657]: Invalid user aquila from 65.203.231.41
auth.log.3.bz2:Nov 23 11:22:12 delly sshd[66933]: Invalid user archie from 65.203.231.41
auth.log.4.bz2:Nov 23 04:22:52 delly sshd[65094]: Invalid user anahid from 65.203.231.41
auth.log.4.bz2:Nov 23 05:32:46 delly sshd[65407]: Invalid user andra from 65.203.231.41
auth.log.5.bz2:Nov 22 23:00:09 delly sshd[63393]: Invalid user alisha from 65.203.231.41
auth.log.6.bz2:Nov 22 12:41:17 delly sshd[60534]: Invalid user abraham from 65.203.231.41
auth.log.6.bz2:Nov 22 16:14:07 delly sshd[61564]: Invalid user africa from 65.203.231.41
auth.log.7.bz2:Nov 22 11:48:33 delly sshd[60289]: Invalid user aaralyn from 65.203.231.41

-su-2.05b# bzgrep '123.14.10.64' auth.log.* | grep 'Invalid user' | wc -l
19
-su-2.05b# bzgrep '200.170.141.134' auth.log.* | grep 'Invalid user' | wc -l
6
-su-2.05b# bzgrep '80.51.31.84' auth.log.* | grep 'Invalid user' | wc -l
3
-su-2.05b# bzgrep '200.157.176.13' auth.log.* | grep 'Invalid user' | wc -l
4


So, someone appears to have a pool of compromised machines and is using each one in a scaled SSH brute force attack, based on the referenced user accounts being bruteforced. I'm seeing more of this than standard, blatant SSH BF attempts. I'll be checking Denyhosts' website to see if they've a resolution on how to track and ban such activity.
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