Which security condition does an attacker exploit when sending a flood of packets to a victim to disrupt services?

The scenario described involves an attacker overwhelming a target system with an excessive volume of packets. This type of attack aims to exhaust the resources of that system, making it unable to respond to legitimate requests, which directly aligns with the characteristics of a Denial of Service (DoS) attack.

In a DoS attack, the attacker seeks to disrupt the normal functioning of a service or network by flooding it with requests or data, thereby rendering it unavailable to its intended users. This exploitation of system vulnerabilities—specifically the system's inability to manage the spike in traffic—illustrates the essence of a DoS attack.

Other options mentioned involve different methods of attack. Phishing is primarily focused on tricking users into providing sensitive information, such as passwords, by masquerading as a trustworthy entity. A man-in-the-middle attack intercepts and potentially alters the communication between two parties. SQL Injection targets database-driven applications by sending malicious SQL commands to manipulate the database. Each of these is distinct from the flooding technique employed in a DoS attack, underscoring why the identified answer accurately reflects the security condition in the original question.