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7. Perform Buffer Overflow Attack to gain access to a Remote System

In this practical, we will perform a buffer overflow attack to gain access to a remote system. Buffer overflow is a vulnerability in which a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory locations.

Step 1: Setting up the Environment​

  1. Ensure that you have a vulnerable program running on the remote system. For this practical, we will use a simple C program with a known buffer overflow vulnerability.

Step 2: Identifying the Vulnerability​

  1. Use a tool like GDB (GNU Debugger) to analyze the vulnerable program. Look for functions that do not check the size of input data before storing it in a buffer.

Step 3: Exploiting the Vulnerability​

  1. Write a script that sends more data to the vulnerable program than it can handle. This will cause the buffer to overflow and overwrite adjacent memory locations.
  2. In the overflow data, include a shellcode that opens a shell when executed. Make sure to overwrite the return address of the vulnerable function with the address of your shellcode.
  3. Run the script against the vulnerable program. If everything goes as planned, you should gain access to a shell on the remote system.

Step 4: Post-Exploitation​

  1. Once you have gained access to the remote system, you can perform various actions depending on your objectives. For example, you can exfiltrate sensitive data, install a backdoor for future access, or use the compromised system as a launchpad for attacks against other systems.

Remember, ethical hacking is all about testing the security of systems with the permission of the owner. Never engage in malicious activities.