What involves sending OS commands through a form and adding code for malicious purposes?

The correct response to the question pertains to Command Injection, which involves sending operating system commands through a web form or web application input with the intention of executing those commands on the server. This type of attack occurs when an application does not properly validate or sanitize user inputs, allowing an attacker to insert or "inject" arbitrary commands that the operating system will execute.

In the context of Command Injection, the attacker can exploit vulnerabilities in the application to execute unauthorized commands, potentially gaining access to the system, modifying files, or performing actions that the original intended functionality of the application should not allow. This can lead to severe security breaches, including data theft or full control of the server.

Understanding Command Injection is crucial for developers and security professionals to enhance their web applications’ security by implementing proper input validation, output escaping, and least-privilege principles when executing commands. This allows systems to mitigate risks associated with this kind of attack by ensuring that the applications do not execute unexpected or malicious commands that may originate from user input.