Hacking Archives - Page 22 of 33 - Hackercool Magazine

Posted on July 27, 2021June 14, 2023 by kanishka10 — 1 Comment

GNU Debugger : Step By step Guide

Hello aspiring ethical hackers. In this howto, you will learn about GNU Debugger, step by step, A debugger is a computer program used to test the working of and debug other programs. Debugging means breaking down the program to see if it has any bugs or working glitches. These bugs can also be vulnerabilities although most of the times they are random behavior or unexpected behavior of the program (like crashing).

A debugger does debugging by running the target program under controlled conditions. GNU debugger more popular as GDB, is one such debugger. It can do four main things for us : Starting the program we want to test, Stop the program at certain points, examine what has happened when the program has stopped and change things in the target program allowing us to experiment. It is a portable debugger and runs on Windows, UNIX and Mac OS X. It can be used to debug programs of the given programming languages below.

1. Ada 2. Assembly 3. C 4. C++ 5. D 6. Fortran 7. Go 8. Objective-C 9. OpenCL 10. Modula-2 11. Pascal 12. Rust

Now let’s learn about this tool practically. We are doing this on Kali Linux OS (any version) as GNU debugger is provided by default in it. We create a new directory named “C” and move into that directory.

In that folder, use your favorite text editor to create a script named “first.c” and code a C program as shown below (Type it, don’t copy, you will thank us later).

As can be seen, it is a simple C program that adds two numbers given to it. Once the program is finished, save the file and compile the program using GCC compiler as shown below. Compiling the program is the process of turning it into machine language. This can be done using command gcc first.c -g -o first.

The “-g” option enables debugging. Once it is in machine code, we can execute it and see if it is working. It can be done in Linux as ./first. As we coded it, the program first asks the user to enter the first number. Once it is over, it asks user to enter the second umber. When both numbers are entered, it will ad -d them both and print the result after adding them both.

The program is running smoothly as intended. Now, let’s load this in the gdb debugger as shown below.

Now let’s run the program once again inside the debugger. This can be done either using command r or run.

Now, in case you forgot the code of the program and can’t remember what it does you have no need to go out of the debugger. Using “l” or “list” command will show the first 10 lines of the code as shown below.

Now let’s add a break point at a certain line of the program. Break points allow us to stop the program at a certain point we want. A break point can be added using command “break” or “b“. Run the program again to see if the program stops at the intended point.

It stops exactly at line 9. The disable command disables the latest break point.

Now we set a break point at line 10 and want to see something. As the program stops at line 10, we can only enter one value that of variable “a”. We can use the print command to see the values of variables we have assigned.

While the value of “a” is something we set and it displaying correctly, we did not yet set the value for variable “b”. But it is still showing some random value. We can change the values we already set using the “set” command as shown below.

We set another break point and all the breakpoints set to the program can be seen using command “info b“.

Although there are three breakpoints, see that only two of them are active as we disabled one already. Let’s run the program again.

It stops at the break point which is at line 10. To completely remove the breakpoint use command “clear“.

Now there are only two breakpoints. To continue running the program from this point, use command “continue“. This will run the program from the exact point where it stopped. The program exited normally. “clear” command can be used to delete break points using their line number as shown below.

Let’s run the program again after removing all the break points .

Now, let’s set three new break points again on lines 9, 11 and 16. We will assign the values as the program executes.

At the first break point, I set the value of variable “a” to 19.5 and continue the program. I use the print command to see the value of variable “a”.

As you can see, it is printed as 19 and not 19.5. Our first bug. Similarly the “b” variable is 17 whereas we gave it the value of 17.6.

When we continue the program as it is, the answer we got is 32786 which is definitely wrong. Here we detected that the program is behaving abnormally when decimal numbers are given as input.

Here’ s another example.

Seeing this we can conclude that this program is only suitable for non decimal numbers and result goes wrong even if one of them is a decimal number. Using gdb we found out our first bug in a program. We can even see the assembly code of this program using the “disass” command.

But more about this in our future articles, That was all about Gnu debugger.

Posted on March 22, 2021June 14, 2023 by kanishka10 — 1 Comment

Donut shellcode generator

Donut shellcode generator is a tool that generates shellcode from VBScript, JScript, EXE, DLL files and DOTNET assemblies. Although there are many tools that can do this, Donut does this with position independent code that enables in-memory execution of the compiled assemblies. This compiled shellcode assembly can either be staged from a HTTP server or embedded directly in the file itself. After the compiled shellcode is loaded and executed in memory, the original reference is erased immediately to avoid memory scanners.

The features supported by the Donut generator are

Compression of the generated files with aPLib and LZNT1, Xpress, Xpress Huffman.
Using entropy for generation of strings 128-bit symmetric encryption of files.
Patching Antimalware Scan Interface (AMSI) and Windows Lockdown Policy (WLDP).
Patching command line for EXE files.
Patching exit-related API to avoid termination of host process.
Multiple output formats: C, Ruby, Python, PowerShell, Base64, C#, Hexadecimal.
What exactly is shellcode? Shellcode is a bit assembly code or machine language. Shellcode plays a very important role in cyber security. Typically shellcode is used in offensive penetration testing. In this article, let us learn about this awesome tool. This tool can be installed in Kali Linux by cloning it from Github as shown below. This will create a new directory named “Donut”

Navigating into the Donut shellcode generator directory, let’s create the shellcode of mimikatz.exe as shown.

Mimikatz.exe is a simple tool that is used to play with windows security. If you take this executable of Mimikatz into a Windows system, any antivirus or Windows Defender will detect this as malware. Just try it on your machine first before turning it into shellcode. It is found in Kali Linux. Here we copied it into the Donut folder.
When we run above command, shellcode is created as a file named “loader.bin” in the same directory of Donut.

By default, Donut creates shellcode for x86 (32bit) and amd64 (64bit). To create only a x86 shellcode, the command is as shown below.

The “-b” option is used to set the shellcode’s behavior when faced with AMSI/WLDP. Anti Malware Scan Interface and Windows Lock Down Policy are security features. These both features help in defending against malware.

By default, Donut sets the shellcode to bypass AMSI/WLDP. By setting the “-b” option to “2” as shown in the above image, it can be set to ABORT once it encounters AMSI/WLDP. Setting “1 ” will do nothing.
Entropy in general terms means the degree of randomness. It is used in malware to make detection of its code harder by Anti malware. This is called obfuscation. The more the entropy the least chances of detection of malware. Donut by default sets random names and al- so encrypts the shellcode to obfuscate the code from anti malware. It can be changed using the “-e” option. Setting it to “2” just sets random names to the payload and setting it to “1” does nothing.

Not just binaries, we can create different output formats with Donut although by default it creates a binary payload. The “-f” option is used to set different output formats. For example, set -ting “-f” option to “2” gives a base64 format. 3 creates C, 4 creates Ruby, 5 creates Python, 6 creates Powershell, 7 creates C# and 8 creates Hexadecimal shellcodes respectively.

The “-z” option is used to setting packing and compressing engines. Donut doesn’t use any compression by default. However it supports four compression engines. 2=aPLib, 3=LZNT1, 4=Xpress, 5=Xpress Huffman. Only the aPlib compressor works in Linux. Rest of them work in windows. Compression reduces the size of the payload whereas packing is used to avoid detection by anti malware.

We have seen that by default, Donut saves the payloads it creates in the same directory. The location as to where the payload is saved can be changed with the “-o” option.

That’s all about the Donut shellcode generator, readers. We will learn more about this tool and how it is used in real world ethical hacking.

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Posted on March 30, 2020June 14, 2023 by kanishka10

Hacking ProFTPd on port 2121 and hacking the services on port 1524

In our previous article, we have seen how to exploit the rexec and remotelogin services running on ports 512 and 513 of our target Metasploitable 2 system. In this article, we will be hacking proftpd on port 2121 and the service running on port 1524 which are next in the Nmap scan report as shown below. On running a verbose scan, we can see that the service running on port 1524 is Metasploitable Root shell.

What is this Root shell? In our Metasploitable Tutorials, we have seen a number of ways to gain a shell or meterpreter session on the target system. But those shells were obtained by hacking some software present on the system. This shell is deliberately left on the system. But why would someone leave a shell deliberately on a system?
In cyber security, there is a concept called trapdoors or backdoors. As soon as hackers gain access to a system by hacking something on it, they plant an easy and quick method to once again come back into the system. This is known as trapdoor or backdoor.

The shell on port 1524 is a shell like that. Usually to prevent other hackers from gaining access to the system through their backdoor they use protection like passwords etc. Here it seems the hacker forgot to secure it. Normally backdoors like these are enabled on some common ports which evoke less suspicion from cyber security personnel. But how do we gain access to this shell? Although there are a number of ways to do this, the easiest way is telnet.
Open telnet and telnet to the port 1524 as shown below. As you can see highlighted below, we got a shell with Root access without doing much.

Try out some linux commands to verify we got a shell with some interaction.

As you can see in the above image, we have shell with ROOT privileges. We can even change the target system’s password now. Now let’s move on to hacking ProFTPd.
Verbose scan has reported that a FTP server named ProFTPd server version 1.3.1 is running on port 2121. I googled for any vulnerabilities present in the particular version but got none. If you remember, we already hacked one FTP server running on port 21.
I used banner grabbing method of telnet (we showed you in detail about this method in of our Hackercool magazine) to see if the service will reveal any more information about itself. It gave nothing except the usual one.

The usual banner grabbing was not working. But maybe we don’t require a banner.We already have it. So this time, I just tried to connect to the service using telnet (although you can also use FTP for this). When “Escape character is ‘^]’ ” message is displayed, I type command “help”. As expected, it gives me all the commands that can be used. So it seems we already have access to the target server.

To confirm this, I tried one command. It prompted me for username and password. But thanks to an excellent phase of enumeration we performed, we already have the username and password. I decided to try the username/password msfadmin/msfadmin. Voila, it worked and we have access to the system now. Typing PWD command gives me the confirmation that I am inside the system. That’s all with hacking ProFTPd.

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Posted on March 13, 2020June 14, 2023 by kanishka10 — 3 Comments

Hacking Rlogin and Rexec Services

In this post, we will be hacking rlogin (remote login) , rexec and remote shell services running on ports 512, 513 and 514 of Metasploitable 2 respectively. Performing a verbose scan on the target gives me the result as shown in the image below.

Before we exploit these services, let me explain as to what these services are. Remote execution service popularly called Rexec is a service which allows users to execute non-interactive commands on another remote system. This remote system should be running a remote exec daemon or server (rexecd) as in the case of our Metasploitable 2 target here. By default, this service requires a valid user name and password for the target system.(For your information, we already have the credentials which we acquired during enumeration).
Rlogin or Remote Login service is a remote access service which allows an authorized user to login to UNIX machines (hosts). This service allows the logged user to operate the remote machine as if he is logged into the physical machine. This service is similar to other remote services like telnet and SSH. This service by default runs on port 513.
Rsh or Remote shell is a remote access service that allows users a shell on the target system. Authentication is not required for this service. By default it runs on port 514.

Although Rsh doesn’t require a password, it requires the username belonging to the remote system. As discussed above, we already have the credentials. In case we don’t have the credentials, we have to crack the passwords as explained in one of our previous posts.
Rsh daemon can be installed in the Kali Linux machine using the command apt-get install rsh-server. Once the installation is over, the below command can be used to get a shell on the target machine. I have tried this with the username root. As you can see, we successfully got a shell on the target system.

The next service we will target is Remote Login running on port 514. The command to get remote login is given in the image below.

As you can see, we once again got a shell on the target system. Using Rexec is also almost similar to the methods shown above. That was about hacking rlogin, rexec and remote shell services. Learn how to hack ProFtpd service.

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Posted on May 2, 2018February 27, 2024 by kanishka10

PEframe : Analysis of portable executable files

Hi Readers today we will see a PEframe Tutorial. These days hackers are using numerous ways to get into our systems. One of them is by sending a malicious portable executable file to us or make us download the malicious executable file and execute it on our system. We have seen one such Real World Hacking Scenario in the issue of Hackercool February 2017. In this scenario we have not only seen how hackers can make malicious executable files but also how they bypass antivirus and convince the innocent users to click on those malicious files. In this howto, we will learn how to perform analysis of portable executable files.

Analysis helps us to determine what the file was intended to do once clicked. There are two types of analysis: static analysis and dynamic analysis. In static analysis the sample is analyzed without executing it whereas in dynamic analysis the sample is executed in a controlled environment. Static analysis is performed on the source code of the sample portable executable. There are various tools which help us in static analysis of portable executables. One such tool is PEframe. PEframe reveals information about suspicious files like packers, xor, digital signature, mutex, anti debug, anti virtual machine, suspicious sections and functions and much more. PEframe is open source and can be installed in Kali Linux as shown below.

Open a terminal and type the command as shown below to clone PEFrame from Github.

After PEFrame is cloned successfully, a new directory is formed with name peframe. You are automatically taken into this directory. This tool requires simplejson (a subset of JavaScript). So install it using pip command. Next, we need to run the setup.py file from the directory. Since it is a python file, we need to run the command “python setup.py” install to install PEframe.

Once the installation is finished, type command “peframe -h” to see its simple usage

Before we analyze the portable executables, let us analyze some files we created for tutorials of our magazine. The first one is msf.pdf we created using Metasploit.

As you can see in the above image, we found not only an IP address but also an url hosting some executable file. It can be assumed that as we open this pdf file, another executable will be downloaded from the IP address and executed in our system. Let us now analyze a hta file created with Metasploit next. This file is analyzed as a HTML document with IP address and it has a library called kernel32.dll. This file probably opens a payload when clicked upon. Given below is another similar file in visual basic format.

Given below is a macro file. You can see all these files have an IP address where probably a listener is running.

Now let us analyze a portable executable file. Kali Linux has some exe files already stored in its windows-binaries folder. We will analyze the plink.exe file.

Plink.exe is a command line utility file similar to UNIX ssh. It is mostly used for automated operations. As you can see in the image given above, the program is giving more detailed information to us than the other files. The plink.exe has four sections and none of them appears to be suspicious. But the file has a packer, mutex and antidbg. The packer it used is Microsoft Visual C++ which is normally used for genuine programs.

Given above is its Antidbg and Mutex information. The dynamic link libraries it imports is also given. Given below are the apis (application programming interfaces) used by the file.

The filenames found in the portable executable are given in the image below. As you can see it has a big list of filenames.

Metadata is data about the data. Metadata reveals a lot of information about a file. Given below is the metadata of our portable executable. We can see that it is a part of Putty Suite.

Even the description of the file is given. Normally malware does not contain so much information about itself like this Plink file. Only genuine files contain so much information because they have no use to hide themselves. Now let us analyze another file. This file is also present in Kali Linux and it is a keylogger. It is klogger.exe present in the same windows-binaries folder.

As you can see in the above image, the file which has five sections has two suspicious sections and the packer it uses is ASPack v2.11. Let us have a look at its suspicious sections once.

Given below in the image are its api alerts and filenames. As you have observed, this file reveals very less information than the previous analyzed file. This in itself does not mean that the file is malicious but it gives a general idea about it. That’s all about Forensics using static analyzer PEFrame. We will be back with a new tool in our next howto.

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Category: Hacking

GNU Debugger : Step By step Guide

Donut shellcode generator

Hacking ProFTPd on port 2121 and hacking the services on port 1524

Hacking Rlogin and Rexec Services

PEframe : Analysis of portable executable files

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