To answer this question, you need to understand how attackers exploit web application vulnerabilities. Let's go through each option to understand why it is correct or incorrect:
Option A) By hacking the firewall - This option is incorrect because hacking the firewall is not directly related to exploiting web application vulnerabilities. Firewalls are responsible for filtering network traffic and protecting the network from unauthorized access, but they do not directly impact web application vulnerabilities.
Option B) By installing viruses on the user's machine - This option is incorrect because installing viruses on the user's machine is a method of attacking the user's device, not specifically exploiting web application vulnerabilities. While malware can be used to exploit vulnerabilities in web applications, it is not the primary method used by attackers.
Option C) By sending malicious HTTP requests - This option is correct because one common way attackers exploit web application vulnerabilities is by sending malicious HTTP requests. By crafting malicious requests, attackers can exploit vulnerabilities such as SQL injection, cross-site scripting (XSS), or remote code execution to gain unauthorized access or control over the web application.
Option D) By sniffing the traffic between a user and the web server - This option is incorrect because sniffing the traffic between a user and the web server is a method used to capture and analyze network traffic. While it can be used to gather information to aid in an attack, it is not the primary method for exploiting web application vulnerabilities.
The correct answer is C) By sending malicious HTTP requests. This option is correct because it describes one of the primary methods used by attackers to exploit web application vulnerabilities.