Tag Archives: Incident Handling and Hacker Techniques

Feb 11 2015
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Incident Handling and Hacker Techniques, Intrusion Analysis, Penetration Testing

Security Hands-On-Training – Part 6 – Final

The previous blog post illustrated how someone with malicious intent could pull off a way to compromise a system. It starts by gaining access to the system using a SQL injection. After the initial access a foothold is established. Then the position is strengthen by uploading the tools of choice. Next the privileges are escalated and a shell with full systems privileges is gained.

However, this attack method might seem complex it would probably happen in case there is a motive or incentive for the attacker do it. An incentive to do such activity could be to steal trade secrets, intellectual property, credit cards or any other information that the attacker could monetize. Nonetheless, there are other motives that serve as an incentive for an attacker to compromise a system. Brian Krebs, a former Washington Post reporter, has putted together a great chart listing the various ways the bad guys can monetize hacked systems (Krebs, 2012).  One of the attack methods that tend to gain popularity is to use SQL injection for malware distribution. Basically, by introducing malicious code in the web server an attacker can turn the web server in a mechanism to deliver malicious code to browsers by taking advantaged of client-side vulnerabilities against unpatched browsers. This mechanism was used by the Asprox botnet (Borgaonkar, 2010) (Pelaez, 2008).  More recently this attack gained the connotation of watering hole or strategic web compromise when it targets a trustworthy web site (Kindlund, Caselden & Chen, 2014). Steven Adair and Ned Moran explain it perfectly in his article about trusted websites delivering dangerous results (Adair & Moran, 2012).

How does an attacker performs this? What are the mechanics behind such method? As the reader noticed in the previous attack scenario there were some key aspects that would be important for the attacker to be successful. One item is the xp_cmdshell stored procedure being enable or the ability to have an out-of-band channel to accelerate the speed of the time based SQL injection technique. But, in the watering hole attack scenario there is no need of any of those factors. The attacker will only need a SQL injection point and from there it can inject malicious script that will be appended trough out the database. As consequence, when a user browses to the web page, the data is retrieved from the database and rendered in the browser. Then the malicious code is executed putting him at mercy of all kind of client-side exploits.

Figure below illustrate these steps using a SQL statement that is famous due to the Asprox Trojan (Analysis, 2008) (Shin, Myers & Gupta, 2009). It  uses a special table in the SQL server sysobjects and syscolumns in an attempt to get access to the “user” defined tables and fields in the website’s database. Through a loop it goes through every table columns and appends a string containing the malicious <script> tag.

This SQL statement is encoded in a hex format and inserted into another SQL statement in order to evade defenses.  The reader can practice this technique and use SQLmap to invoke a SQL shell that allows to execute SQL statements.  Then this prepared statement is executed which will result in infecting the database data. For reference a picture of what DBA will see if he looks into is affected database is also shown.

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From this moment onwards the web server is infected. When a user goes in and browses trough the infected web pages it will download and execute the evil Java Script within the <> tags (Stuck, 2009) (Mendrez, 2009). This evil script can do, among other things, scan the visitor machine for client side vulnerabilities and deliver the appropriate exploit payload. Similar to using guided missiles this attack can be very effective and is worth to mention James Lee presentation “Using Guided Missiles in Drive­bys  at Defcon 17“.

As demonstrated using this environment the reader could get a practical understanding of how a typical watering hole attack is executed. The next step might be to explore the client side vulnerabilities and exploits by taking advantage of the evil script that is inserted into the database.  The reader is encouraged to further learn, practice and explore this vector of attack with tools such as the Browser Exploitation Framework (BeEF) developed by Wade Alcorn and others, or  the Social Engineering Toolkit (SET) from David Kennedy.

Continuing the Journey

Even though the tools used are extremely functional and almost no knowledge is needed to run an exploit against a vulnerable server using SQLmap or Metasploit this is the first step in building hands-on information security skills. Some techniques used are low hanging fruit. Nonetheless, the reader should start with them in order to advance to more complex methods and techniques using incremental approach.  A proposed next step would be to further expand this environment to model business networks with end point and boundary defenses such as a Proxy, an IDS/IPS, a HIDS, etc. Also introduce Linux based systems such as an e-commerce and test other techniques and exploits (Rocha, 2012). As well, the reader could create scenario based challenges and simulations like Ed Skoudis promotes on his presentation “Using InfoSec Challenges to build your skills and career” that can emphasize the development of critical thinking (Skoudis, 2012).

Further practice reconnaissance, scanning, exploitation, keeping access and covering tracks will be doable. In addition to offensive skills the reader might want to practice defensive skills. When the attacker launches a specific technique  how does it look like? Which opportunities does it bring from a defender to identify and detect it from the network or database level? How does it look at the operating system level. How would the reader be able to better prepare, identify, contain, eradicate and recover from each one of these and other attack scenarios. Could the correlation between the logs from the DNS server and Database server be used to detect such incident? Which IDS signatures would be needed to detect this kind of traffic? This and other suggestions have been also encouraged throughout the previous chapters.

It’s this never ending cat and mice game which makes our industry a very interesting place to be at. Like when playing a game, It involves defenders trying to build a secure system, then how to innovate, progress and take it to the next level by circumvent those measures using different tools and techniques. Then the defender improves the system and so on. This healthy competition between the attacker and the defender will make us smarter and better at security. As Jon Erickson mention on his book “The net result of this interaction is positive, as it produces smarter people, improved security, more stable software, inventive problem-solving techniques, and even a new economy”.

Conclusion

Although there are plenty of books and open source information that describe the methods and techniques demonstrated, the environment was built from scratch.  The tools and tactics used are not new. However, they are relevant and used in today’s attacks. Likewise, the reader can learn, practice and look behind the scenes to better know them and the impact they have.

The main goal was to demonstrate that hand’s on training is a very valuable and cost efficient training delivery method that allows a better practical understanding on security. This method has advantages to build up your skills – not only from an incident handling and hacking techniques perspective but also from a forensics perspective.  One can practice and improve their ability to determine past actions which have taken place and understand all kinds of artifacts which occur within the outlined scenarios. For instance, one could simulate an actual forensic investigation!  On the other hand, from an Intrusion Analyst’s perspective the reader can capture the full contents of the network packets during the exercises and work on mastering his TCP/IP and intrusion detection techniques. In addition to that, the data set can be also feed to intrusion detection devices in order to measure how effective will they be in detecting the attacks.

Practice these kind of skills, share your experiences, get feedback, repeat the practice, grow to be proficient,  improve your performance and become fluent.

 

 

References

Krebs, B. (2012, 10 15). The scrap value of a hacked pc, revisited. Retrieved from http://krebsonsecurity.com/2012/10/the-scrap-value-of-a-hacked-pc-revisited/)
Borgaonkar, R. (2010). An analysis of the asprox botnet. Manuscript submitted for publication, .
Pelaez, M. (2008, 8 15). Obfuscated sql injection attacks. Retrieved from https://isc.sans.edu/diary/Obfuscated SQL Injection attacks/9397
Kindlund, D., Caselden, D., & Chen, X. (2014, 02). [Web log message]. Retrieved from http://www.fireeye.com/blog/uncategorized/2014/02/operation-snowman-deputydog-actor-compromises-us-veterans-of-foreign-wars-website.html
Adair, S., & Moran, N. (2012, 05 12). [Web log message]. Retrieved from http://blog.shadowserver.org/2012/05/15/cyber-espionage-strategic-web-compromises-trusted-websites-serving-dangerous-results
Analysis, X. (2008). Asprox trojan and banner82.com . Retrieved from http://xanalysis.blogspot.ch/2008/05/asprox-trojan-and-banner82com.htm
Shin, Y., Myers, S., & Gupta, M. (2009). A case study on asprox infection dynamics. Manuscript submitted for publication, Computer Science Department, Indiana University, .
Stuck, F. (2009). An overview of a sql injection attack. Retrieved from http://geek37.net/Portfolio_SQL_Injection_Presentation.html
Mendrez, R. (2009). Another round of asprox sql injection attacks. Retrieved from http://labs.m86security.com/2010/06/another-round-of-asprox-sql-injection-attacks/
Rocha, L. (2012, Nov 23). Hands-on lab – ecommerce – part 1. Retrieved from https://countuponsecurity.com/2012/11/23/hands-on-lab-ecommerce-part-1/
Skoudis, E. (2012, March). [Web log message]. Retrieved from https://blogs.sans.org/pen-testing/files/2012/03/Put-Your-Game-Face-On-1.11.pdf

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Jan 26 2015
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Incident Handling and Hacker Techniques, Intrusion Analysis, Penetration Testing

Security Hands-On-Training – Part 5

[Now that we have the environment ready we can start looking at the different attack methods. The goal is to practice the tools, look behind the scenes and understand the techniques that might be used to gain access, establish a foothold, escalate privileges, steal credentials and exfiltrate data. With this one can learn, practice and gain a better practical understanding on security. ~Luis]

Ed Skoudis describes the anatomy of an attack using a 5 step model. The steps are reconnaissance, scanning, exploit, keeping access, and covering tracks (Skoudis & Liston, 2005). In our environment, the reconnaissance and scanning steps are skipped. The focus will go be on the exploit phase. A sophisticated intruder will spend a great amount of time and resources performing reconnaissance and scanning.

We will use SQL Injection as an example and utilize SQLmap in this exercise. SQLmap has been developed by Bernardo Damele A.G. and Miroslav Stampar and it is an actively maintained and powerful command line tool. It is available as part of the BackTrack and Kali distribution (SQLmap).

Start by getting the latest version of SQLmap from the repository by issuing the command shown below.

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To configure SQLmap, we will tweak the default settings. In order to get those settings the reader should access the test site through a proxy like Paros or use the Firefox tamper data plug-in. Save all the POST parameters in a file which will be used as payload. The nest figure shows the steps taken to retrieve the POST parameters and use them.

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Then execute SQLmap.  It will determine that the parameter ctl00$ContentPlaceHolder1$descriptionTextBox is vulnerable using a time-based blind SQL injection technique. Using this technique the tool is able to extract the SQL query results in a bit-by-bit manner (Litchfield, 2005). Asking questions to the database and observing how it reacts to those questions will allow the attacker to infer the value of the data (Stampar, 2009) (Litchfield, 2005).

Now that the reader has a method that works and that allows him to have access to the system, the reader can move to more advanced techniques. Figure below exemplifies in detail how SQLmap achieves an operating system shell using time-based blind injection techniques. It starts by determine if the current user is part of the sysadmin role. Then it determines if the xp_cmdshell extended procedure is available. This stored procedure is one of the most powerful stored procedures and it is used to launch operating system commands in the context of the SQL server service (Litchfield, Anley, Heasman & Grindlay, 2005). In this case it was not available so SQLmap has the ability to re-enable it using the sp_configure stored procedure. The reader needs to have sysadmin rights to the DB to use sp_configure. With xp_cmdshell, the reader can start executing operating system commands using SQL statements. Because the results of the xp_cmdshell are not sent to the client, further queries using temporary tables are used to retrieve the results.

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SQLmap is able to retrieve data over out of band channels such as DNS. This technique allows the retrieval of the SQL results using a DNS recursive resolution process which is much faster than the time-based or boolean-based inference methods (Stampar, 2009). To accomplish this, the attacker needs to control a DNS domain name. Of course the database server also needs to have a dns server configured and be able to perform queries.

The DNS requests made by the database will be triggered by SQL queries. Due to the way DNS works, if the database does not know the answer, it will forward the request to the upstream DNS server. In our environment ,the system does not have access trough the firewall for any outbound communications. Nevertheless, it can forward the DNS requests to the DNS server which in turn forwards them to the authoritative server which is under the attacker’s control. Sensepost presented at BlackHat USA 2007 a SQL injection tool called Squezza that was able to extract data trough DNS and others channels (Research, 2007). This technique was added to SQLmap in 2012 (Stampar, 2009). To carry out this technique, SQLmap will be executed with a command line option that specifies the domain name controlled by the attacker. Figure below shows the command executed, the SQL queries performed, and the output of the commands. It also shows how the DNS queries are constructed.

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After executing this technique, a low privilege shell is gained. The next step will be to strengthen the position within the target by uploading additional tools to the system to escalade privileges. In addition, since it is known the system can communicate via DNS, a different set of tools will be used to take advantage of this and further compromise the system. This combined arms approach will result in use getting a “system” privilege shell back via DNS.

To escalate privileges a tool called churrasco developed by Cesar Cerrudo is used. This tool takes advantage of an exploit that uses a technique that he named as token

kidnapping which elevates privileges to a System account by using techniques that impersonate tokens to manipulate processes and thread access lists (Cerrudo, 2008). The source code of the tool that affects Windows 2008 was downloaded from Cesar Cerrudo’s website and compiled using Visual Studio C++ 2008 Express edition (www.argeniss.com/research/Churrasco2.zip). It is important to note that this vulnerability has been patched by Microsoft in Windows 2012 (MS09-12). The exploit when executed successfully will span a shell to an IP and port chosen by the user.  In spite of this, because the firewall does not allow the target system to communicate with the outside world, the shell will communicate back to the attacker through DNS. We will use dns2tcp. This tool allows relaying TCP connections trough DNS. This way the spanned shell from the exploit will be redirected and forwarded using DNS (Dembour).

These tools will be uploaded to the system, written to the file system in a directory where the low privilege account would have write access and then executed. To accomplish this the reader starts by uploading the dns2tcp client tool ( dns2tcpc.exe) using  SQLninja, a powerful SQL injection tool created by Icesurfer (SQLninja). The same way SQLmap needed configuration settings, SQLninja will need the target details, the injection point and a well formed HTTP request. This is done via SQLninja.conf and the HTTP POST request used is shown in the next figure.

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The methods used by either SQLmap or SQLninja to upload files and write them to the file system using SQL injection are based on the xp_cmdshell procedure. This procedure can facilitate the creation of files by using the “>>” redirect operator (Clarke, 2012). Behind the scenes SQLninja can use two techniques to upload files to target systems. One technique is to base64 encode the binary and then upload it. The other technique uses an old trick to convert the binary into a DEBUG script.  The default technique is to use the base64 method and it can be defined in the sqlninha.conf by stating “upload_method = vbscript”.  Figure 22 illustrates this technique.

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This technique works well. The alternative technique creates a DEBUG script which can be passed to the debug.exe script to be converted to a binary. The following picture shows the steps taken by SQLninja to accomplish this.

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Compared to using a Base64 encoded binary, this technique has the disadvantage that debug.exe can only build executables smaller than 64 Kb. However, you can split bigger files into 64 KB portions and after uploading them you can concatenate them together using copy /b portion _1  + portion_2 original-file.exe (Clarke,2012).  This technique is slower but as the advantage that debug.exe is available in any windows operating system and therefore the attacker won’t need any additional scripts or tools to create a binary on the target system. More details about debug.exe is available on Kipivirne.com.

In case the reader would like to try the DEBUG technique he can convert windows binaries to a debug script format in Backtrack using a python script called dbgtool.py. Is available  in the SQLmap directory under /extra/dbgtool/. Then the file containing the debug script can be moved to a windows machine and converted back to a binary using the “debug < debugfile” command.

The reader can follow the same process to upload any additional tools. The target system does not use any antivirus tools, but this technique can be performed even with antivirus. The traditional way that antivirus programs identify the presence of a virus is by using signatures (Labbe, Rowe & Fulp, 2006). This can be subverted by using an exploit that the antivirus tool does not have a signature for. One simple way to do this is to use a hex editor to remove the machine code that triggers the signature without having an impact on the execution of the exploit. Another way might be by using encoders or packers or even target the AV software itself (Ormandy, 2012)(Koret, 2014). This is left as an exercise for the reader to further research.

The next tool to be uploaded is churrasco.exe. We need to configure SQLninja to be aware of this tool in order to allow it to be uploaded to the target. This is done by adding lines of code to sqlninja.py to identify the file, and adding the file to the sqlninja/apps folder.

Now that the dns2tcpc.exe and churrasco.exe tools are uploaded the next step is to execute them. Because they need to be executed sequentially, the task scheduler in windows will be used. This can be invoked from the command line using the schtasks.exe command. The schedule of the tools execution will be done using the interactive command line that can be invoked by the SQLmap os-shell feature.

First SQLmap is launched. Then it checks if the files are saved in the %TEMP% folder. Finally, two tasks are scheduled to run daily at pre defined times with current privileges. The first task executed is “dns2tcpc”. The command line instructs dns2tcpc.exe to encapsulate the data using DNS requests to the acme.com domain with using a pre-shared key. In addition, it instructs the server side of the tool to use the ssh resource and to listen for incoming connections on port 137 TCP (Dembour). The second task executed is “churrasco.exe”. The command line instructs churrasco to execute a reverse shell to localhost on port 137 which is where dns2tcpc.exe is listening. These steps are illustrated below.

security-hot-fig23

After successful scheduling the tasks, the reader needs to exit SQLmap to release UDP port 53 (remember SQLmap is using this port while launching the commands trough encapsulated DNS queries). Then it executes the dns2tcp server daemon. This tool is available on the backtrack distribution under /pentest/backdoors/dns2tcp. Before executing the daemon the reader  needs to create a configuration file in the user’s home folder, configuring the IP address and the port to listen on, the domain name send questions to, the pre-shared key, and where to redirect the connections received.  The directory specified in the chroot settings of the configuration file also needs to be created beforehand.

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After defining the configuration file, dns2tcpd is instructed to listen on IP address 192.168.1.7 (-i), execute on the foreground (-F) and show debug level information so the queries and answers can be seen (-d 3). Then the reader will need to wait for the scheduled tasks to kick in.

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While waiting for the scheduled tasks to start, another shell is needed. This shell will listen for an incoming connection on localhost port 22 which is going to be forwarded by our dns2tcp daemon. To do this the Metasploit mutil-handler is used. This will handle the reverse connection but the reader could simple use netcat (nc -l -p 22).

At this stage the attacker has two shells open. One to answer the DNS queries addressed to the domain acme.com. These will contain encapsulated data which are  shell code that is going to be forwarded to port 22. On the second shell there is Metasploit multi-handler waiting for that shell code. When the scheduled tasks triggers a TCP reverse shell with system privileges encapsulated trough DNS data will be opened. The following figure demonstrates how these techniques work together.

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The next picture illustrates a summary of the techniques used.

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Now, that the reader has escalated privileges and maintains access he can steal valid user credentials.  To steal credentials there are a variety of tools and ways. In this case a tool named gsecdump v2.0b5  created by Johannes Gumbel from TrueSec that allows extracting the hashes from SAM or AD database will be used (TrueSec). This tool is uploaded to the target system like it was shows previously. The execution is shown below. With the hashes extracted the reader can then crack them using the John the Ripper or Hashcat. Or, it can use the hashes to further move into the network by using passing the hash or pass the ticket techniques (Rocha, 2012).

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From this moment onwards the reader can further practice tools and techniques to increase his presence in the target, move and compromise other targets in the network, steal and exfiltrate data and finally cover his tracks.

 

References:

Skoudis, E., & Liston, T. (2005). Counter hack reloaded: A step-by-step guide to computer attacks and effective defenses, second edition. Prentice Hall.
Ormandy, T. (2012). Sophail: A critical analysis of sophos antivirus. Retrieved from http://lock.cmpxchg8b.com/Sophail.pdf
Ormandy, T. (2012). Sophail: Applied attacks against sophos antivirus. Retrieved from http://lock.cmpxchg8b.com/sophailv2.pdf
Koret, J. (2014, January 1). . . Retrieved , from http://www.slideshare.net/JoxeanKoret/breaking-av-software-33153490
TrueSec. (n.d.). gsecdump v2.0b5. Retrieved from https://www.truesec.se/sakerhet/verktyg/saakerhet/gsecdump_v2.0b5
SQLmap.(n.d.) Retrieved from http://sqlmap.org/
SQLninja. (n.d.). sqlninja. Retrieved June 7, 2014, from http://sqlninja.sourceforge.net/
Stampar, M. (2009). Data retrieval over dns in sql injection attacks. (Master’s thesis)Retrieved from http://arxiv.org/ftp/arxiv/papers/1303/1303.3047.pdf
Rocha, L. (2014, Jul 2). The path to the Golden Ticket. Retrieved from https://countuponsecurity.com/2014/07/02/the-path-to-the-golden-ticket/
Litchfield, D. (2005, March). Sql injection and data mining trough inference. Backhat europe 2005.
Research, S. (2007). Squeeza. Retrieved from http://research.sensepost.com/tools/servers/squeeza
Cerrudo, C. (2008, 5 17). Token kidnapping. Retrieved from http://www.argeniss.com/research/TokenKidnapping.pdf
Dembour, O. (n.d.). dns2tcpc – a tunneling tool that encapsulate tcp traffic over dns. Retrieved from http://manpages.ubuntu.com/manpages/raring/man1/dns2tcpc.1.html
Clarke, J. (2012). Sql injection attacks and defense, 2nd edition. Syngress.\
Labbe, Keith, Rowe, Neil & Fulp, J.D. (2006). A Methodology for Evaluation of Host Based Intrusion Prevention Systems and its Applications, 2006 IEEE Information Assurance Workshop

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Jan 18 2015
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Incident Handling and Hacker Techniques, Intrusion Analysis, Penetration Testing

Security Hands-On-Training – Part 4

[Following part 3 where the  ASP.NET web site code was modified, part 4 will show different methods, techniques, and ways of manipulating the user input in order to control the logic of the application making the web application exploitable. ~Luis]

During the previous chapter the defenses that were in place in the test application were removed. To achieve this a  trial and error approach was used. While looking for SQL injection vulnerabilities, different methods, techniques, and ways of manipulating the user input were tried in order to see how the system reacted. This method allows us to learn and practice which defenses would need to be removed to allow a successful exploit.

The HelpDesk.aspx page is shown in the next figure. It simulates a helpdesk ticketing system where the user is allowed to input data into two fields. The “Station Number” and the “Problem Description”.

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When the user clicks on the “Submit Request” button, the web form takes the value and passes it to a SQL statement. This will happen without validation controls because they were removed in the previous post. Behind the scenes this page contains an INSERT SQL statement that will receive the user input and insert it into the database. The code block that allows this to happen is shown below.

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The database called “Dorknozzle” contains a table called “HelpDesk”. This is shown in the below figure. In the database there are several columns that are used to store the user input. During the trial and error method to discover a SQL injection point  it was found that input that is stored in the database as an integer could not be manipulated.  This applies to the “Station Number” field. However, the “Description” field uses the nvarchar type and allows up to 50 characters to be inserted.

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With this in mind and with the defenses down the reader can start adding characters in the user input fields that would change the initial query logic and see how the system reacts. The first character to try is the single quote. When clicking the submit button the web application returns a SQL exception message. This happens because the error messages were enabled.

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This was exactly the objective. This SQL error message discloses that the statement submitted had an unmatched number of single quote characters. To further exploit it the reader would need a way to construct a statement in the input field that allowed to terminate the string and append the malicious SQL statement (OWASP,4). At this stage the debug functionality of Visual Studio Express was used. By introducing a break point in the code where the SQL statement is, the application execution could be controlled. Then the Web application was started in debug mode. In the HelpDesk page the character “A” and a single quote was inserted in the “Problem Description” field. When submitting the request the break point kicked in and the step into functionality was used to dig into what was happening. This allows us to verify exactly how the SQL statement was being constructed and executed by the database. The next figure shows these steps.

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The SQL statement that was being sent to the database was not well formed due to the crafted input which caused an odd number of single quote characters resulting in a SQL error. The below figure shows what the SQL statement looks like.

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Now it is just a manner of time to find the correct input that will create a well formed SQL statement and introduce the malicious SQL code. During this iterative process the reader can find that he could close the SQL statement by injecting the right number of values that the database is expecting. Then another statement could be inserted and this would be the injection point and the “–“ sequence (two dashes) can be used to ignore the rest of the statement. This SQL injection point is inside an INSERT statement. Because of this you couldn’t see the output of the injected query or any difference in the in the responses of the web application which increases the difficulty of the technique. Using a technique called Blind SQL injection, which was first introduced by Chris Anley in 2002, the reader  might use inference techniques to get the results (Clarke, 2012). For example, with this technique, SQL statements that analyze the response time can be used. One method is using the sleep function like WAITFOR DELAY ‘time’. Using this technique the reader could make the database wait and reveal if a statement was true or false. In the next figure is shown how the SQL statement would look like after having the evil payload inserted. This will result in the database to wait 5 seconds before producing the results.

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In addition to the previous example the following SQL statements could be used in the SQL injection point to understand how the database would react:

IF (1=1) WAIT FOR DELAY ‘0:0:5’ —
IF (1>2) WAIT FOR DELAY ‘0:0:5’ —

Then more advanced queries could be used to determine if the current user is part of the sysadmin role:

IF((SELECT (CASE WHEN (IS_SRVROLEMEMBER(‘sysadmin’)=1) THEN ‘1’ ELSE ‘0’ END))=’1′) WAITFOR DELAY ‘0:0:5’ –

This seems a rather tedious and slow process but this will be automated using well known SQL injection tools in the upcoming articles. These tools dramatically increase the efficiency of an attacker but also extend the attack population. One disadvantage of these powerful tools is that any inexperienced person can mount complex SQL injection attacks regardless the technique or the database technology (Clarke, 2012).

During this exercise the reader is able to learn about SQL, its inner working queries and how SQL statements are constructed. It should be clear now why is important to disable any error messages and  why it is important to sanitize all input. When the reader has a good understanding of the tools and techniques and can control the logic of the application the reader could also use SQL injection with serious consequences. Tools like SQLmap and SQLninja can be used to automate these techniques.

Even though the focus was on SQL injection the environment is ready for additional tests by reducing our defenses further. In the context of this web application the reader could introduce other vulnerabilities such as Cross-Site scripting (XSS), Cross-Site Request Forgery (CSRF) or introduce a broken authentication mechanism. Learning how to do this and understanding the mechanisms behind the scenes is a rewarding exercising. Likewise, learning the attack vectors, use the tools, taking the time to experiment with them and understand how they work will make one better equipped and skilled.

 

References:
OWASP. (4, September 13). Testing for sql injection (owasp-dv-005). Retrieved from https://www.owasp.org/index.php/Testing_for_SQL_Injection_(OWASP-DV-005)
Clarke, J. (2012). Sql injection attacks and defense, 2nd edition. Syngress.

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Jan 18 2015
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Incident Handling and Hacker Techniques, Intrusion Analysis, Penetration Testing

Security Hands-On-Training – Part 3

[Following part 1 and part 2 where we built an infrastructure with different systems, below article will focus on the Web Stack and will show how the ASP.NET code has been modified in order to make the application less secure. This will allow us to understand the security mechanism enforced by the application in order to make it defenseless and practice our security tools and techniques! ~Luis]

Instead of modifying the secure test application, the reader could use an existing vulnerable web application. Likewise, the reader could use test sites that allow him to practice hacker techniques in a wide variety of security realms. Just chose one from Aman Hardikar’s awesome mind map with various penetration testing practice labs and vulnerable applications (Hardikar, 2013). But on the other hand, building an infrastructure with simple IT services such as directory services, messaging services and a web stack  will allow the reader to enhance the depth and breadth of its skills not only from a security perspective but also from a systems and networking viewpoint.

Also, It is valuable to be exposed to defense and offense. Through the process of creating this environment and then growing it at will, the reader can practice both sides. In this environment a simple and secure web application is created and then its defenses are reduced. For instance, while following the mentioned book to create an ASP.NET website the code uses strong protections against SQL Injection using parameterized queries, stored procedures and data validation controls (Posey, Barnett & Darie, 2011). To make the application less secure, the reader first has to understand the security techniques employed by this application. The same applies to other technologies. For example techniques that protect against malicious user input. Once the code is vulnerable, the reader can explore attack techniques.

After building the mentioned web application – the code is available for free on GitHub -, 4 steps are executed to make it vulnerable: First, a user account with system administration privileges is created. Second,  the SQL parameterized statements are replaced by dynamic SQL statements. Third, the code is changed to make the application disclose error information and finally, the data validation code is removed to avoid input sanitization based on type, length, format or range.

For step one, go into the SQL Management Studio on your database server and create a user with system administration privilege (sysadmin) as illustrated in the left side of the following figure.
security-hot-fig5

This user will be used to define a database connection using SQL authentication. Then start changing the .NET application code using Visual Web Developer 2010 Express. For reference the right side of previous figure shows how these code files look. Next, web.config is modified. The authentication mechanism used by the application to connect to the database will change from integrated authentication to SQL authentication as shown on the left side of below figure (Posey, Barnett & Darie, 2011).  After making the change make sure the application can be compiled and is working as expected. Next change HelpDesk.aspx.cs. Remove the block of code that contains the parameterized SQL statements and replace it with a dynamic SQL as shown in right side of the following figure.

security-hot-fig6

Following that, step three is to customize the Try-Catch-Finally code block in HelpDesk.aspx.cs as shown on the below figure. This allows the web application to throw error messages and disclose them locally. Finally change HelpDesk.aspx and remove input data validation by commenting it out. This will facilitate the attack methods later on. The left side of the below figure shows the code block that should be removed or commented.

security-hot-fig7

In addition,  disable the EnableEventValidation and ValidateRequests directives by setting them to false in the header of the HelpDesk.aspx (see below figure).

security-hot-fig8

By following these steps the reader made the HelpDesk.aspx page vulnerable to SQL injection. This is going to be demonstrated in the next articles. It is not an intent to make the reader a .NET developer. Still, it is up to the reader if  he wants to further read and explore more about what are those measures that were removed or just follow the steps in order to practice the tools and tactics in the upcoming articles.

 

References:
Hardikar, A. (2013, 06). Penetration testing practice lab – vulnerable apps / systems. Retrieved from http://www.amanhardikar.com/mindmaps/Practice.html
Posey, T., Barnett, W., & Darie, C. (2011). Build your own asp.net 4 web site using c# & VB, 4th edition. SitePoint

 

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Jan 03 2013
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Incident Handling and Hacker Techniques

SANS Comes to Zürich Starting January 23

Starting the 23rd of January 2013, I will be mentoring  SANS Security 504: Hacker Techniques, Exploits & Incident Handling in Zürich. The training material is awesome and I am looking forward to start. Below is a short description about this mentoring session.sans-mentor

If your organization has an Internet connection or one or two disgruntled employees (and whose doesn’t!), your computer systems will get attacked. From the five, ten, or even one hundred daily probes against your Internet infrastructure to the malicious insider slowly creeping through your most vital information assets, attackers are targeting your systems with increasing viciousness and stealth.
This course addresses the latest cutting-edge insidious attack vectors and the “oldie-but-goodie” attacks that are still so prevalent, and everything in between. Instead of merely teaching a few hack attack tricks, this course includes a time tested, step-by-step process for responding to computer incidents; a detailed description of how attackers undermine systems so you can prepare, detect, and respond to them; and a hands-on workshop for discovering holes before the bad guys do.

Students on the SANS mentor program study SANS Hacker Techniques, Exploits & Incident Handling course books at their own pace. Each week, students meet with SANS Local Mentor, who will lead class discussions, provide hands-on demonstrations, point out the most salient features, and answer questions. The Mentor’s goal is to help students grasp the more difficult material, master the exercises, and prepare them for GCIH certification.

This challenging course is particularly well suited to individuals who lead or are a part of an incident handling team. Furthermore, general security practitioners, system administrators, and security architects will benefit by understanding how to design, build, and operate their systems to prevent, detect, and respond to attacks.

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Dec 26 2012
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Incident Handling and Hacker Techniques

Honeypot Captures Bad Villain!

On my previous article named Deception Techniques I introduced the concept of Honeypots and illustrated how you could easily run a medium-interaction Honeypot called Kippo. It was highlighted the advantages of running one of these systems. For instance, it could be used to gather intelligence trough the knowledge and information that one could obtain by observing, analyzing and investigating it. To illustrate the intel you can gain, the following facts were captured from a Kippo Honeypot during the first 20 days:

  • 13348 Total break in attempts
  • 667,4 Average break in attempts per day
  • 13290 Unsuccessful break in attempts
  • 2968 Unique account names
  • 8060 Unique passwords
  • 58 Successful break in
  • 71 Unique IPs were used on the 13290 unsuccessful attempts
  • 44 Unique IPs were used on the 58 successful logins
  • 12 Unique IPs logged in and entered commands.
    • Where 8 where from Romania, 2 from Italy, 1 from US and 1 from Germany.

These and other interesting statistics can be visualized using Kippo graph plugin. Or you can query directly on MySQL and produce a tables with the following results, which shows the 12 Bad Villains that successful logged int and entered commands:

IP Country As SSH Client
95.xxx.xxx.xxx Italy AS3269 SSH-2.0-PuTTY_Release_0.62
176.xxx.xxx.xxx Romania AS6910 SSH-2.0-PuTTY_Release_0.62
95.xxx.xxx.xxx Italy AS3269 SSH-2.0-PuTTY_Release_0.62
89.xxx.xxx.xxx Romania AS44203 SSH-2.0-PuTTY_Release_0.62
94.xxx.xxx.xxx Romania AS48161 SSH-2.0-PuTTY_Release_0.62
79.xxx.xxx.xxx Romania AS8708 SSH-2.0-PuTTY_Release_0.62
109.xxx.xxx.xxx Romania AS8953 SSH-2.0-PuTTY_Release_0.62
79.xxx.xxx.xxx Romania AS8708 SSH-2.0-PuTTY_Snapshot_2010_04_07:r8911
188.xxx.xxx.xxx Romania AS8708 SSH-2.0-PuTTY_Release_0.62
38.xxx.xxx.xxx US SSH-2.0-PuTTY_Release_0.60
85.xxx.xxx.xxx Romania AS57568 SSH-2.0-OpenSSH_5.1p1
81.xxx.xxx.xxx Germany AS24961 SSH-2.0-OpenSSH_5.1p1

Other than statistics, Kippo is designed to log the entire shell interaction performed by the attacker plus the archive of any tool they downloaded. From what was observed, after successful login the attacker normally follow the same high level steps:

  • Scanning other systems to identify open SSH ports.
  • Gain access trough SSH brute force.
  • Maintain access by installing rootkits and/or joining the system to IRC Channel.
  • Covering tracks.

Looking deeper into the majority of the attacker sessions, they executed the following actions:

  1. Check the speed of the internet connection by downloading a big file
  2. Check the system Operating System and hardware capabilities
  3. Download necessary tools to :
    1. Perform automated Recon, Scanning and Gain access to other SSH systems via brute force (e.g. gosh) ;
    2. Join the system to an IRC network in order for the system to became part of a larger bot army and wait for attacker commands (e.g. legendbot);
    3. Install IRC proxy/bouncer in order to further hide attacker identity and conceal their IP address when connecting to IRC network and issuing Command & Control commands (e.g. Eggdrop, Emech, Psybnc)
  4. Maintain Access (e.g.Linux user mode rootkits like shv5)
  5. Cover tracks

It is my intention to illustrate these steps and the tools and commands used in further posts. Nevertheless, the following example illustrated the commands issued by one of the attackers in order to cover his tracks:

#unset ; rm -rf /var/run/utmp /var/log/wtmp /var/log/lastlog /var/log/messages /var/log/secure /var/log/xferlog /var/log/maillog ; touch /var/run/utmp /var/log/wtmp /var/log/lastlog /var/log/messages /var/log/secure /var/log/xferlog /var/log/maillog ; unset HISTFILE ; unset HISTSAVE ; unset HISTLOG ; history -n ; unset WATCH ; export HISTFILE=/dev/null ; export HISTFILE=/dev/null

One interesting finding was an attacker that downloaded a bot script written in Perl. The script is called Legend Bot and it consists of 1032 lines of Perl code. It implements a limited set of  features: DDoS attacks (udp floods, sql floods), execution of Linux system, a vulnerability scanner and a Socks proxy. After executed it establishes a connection to a standard IRC network service port, joins the configured attacker’s IRC channel and waits for the attacker’s commands. In this case the IRC channel was hosted at Undernet. For those who don’t know the IRC network Undernet provides a free of charge communication infrastructure which can be misused by attackers to maintain, expand, manage and control their bots army[1].

botmaster

IRC Bot Command and Control

The following picture (nick names removed) illustrates the interaction between a botherder (bad villain)  issuing command and control commands to two compromised systems a.k.a Zombies. This interaction happened on a channel where the chat logs were in  Romanian. First command executed (!legend @system) is used to check the operating system version (uname -a), the system uptime, the name of the process which the bot is running (init[3]) and the user id. Second he checks which  vulnerabilities could be potentially used as local escalation privileges. Third he removes the logs in order to cover is tracks.

After some time finally he launches a UDP Flood DoS attack against a particular system.Interesting that with only 2 systems the attacker can reach easily launch a two digit Megabits DoS attack. This is not shown in the picture but I pasted here the IRC chat logs (IPs removed):

<Botherder> !legend @udp 173.xxx.xxx.xxx 65000 300 22
<Bot1> .:UDP2:. UDP2 Attacking 173.xxx.xxx.xxx:22 with 65000 KB(s) for 300 seconds.
<Bot1> .:UDP2:. UDP2 Attacking 173.xxx.xxx.xxx:22 with 65000 KB(s) for 300 seconds.
<Bot1> .:UDP2:. UDP2 Sent 1275439 Kb in 300 seconds to 173.xxx.xxx.xxx.
<Bot2> .:UDP2:. UDP2 Sent 10581733 Kb in 300 seconds to 173.xxx.xxx.xxx.

Among others, the value of these compromised systems relies on their capability to be as used as vulnerability scanners, anonymity proxies and/or be part of Denial of Service attacks. To further understand the motives and monetary value behind having compromised systems you can read this article from Krebs on Security, or read the book Inside Spam Cartel by Spammer-X.

Learning the techniques of the attackers can be very useful in order to better understand the motives and methods. Plus will allow you to sharpen your intrusion detection, incident handling and forensic skills.

References:

[1] Analysis of Internet Relay Chat Usage by DDoS Zombies, Stéphane Racine, 2004

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