Which of the following types of attacks is targeting a Web server with multiple compromised computers that are simultaneously sending hundreds of FIN packets with spoofed IP source IP addresses?

Evasion attacks are designed to bypass IDS/IPS detection by fragmenting or obfuscating malicious traffic, not to overwhelm a server with volume.

Insertion attacks trick an IDS into processing packets that the end host rejects, exploiting TTL or checksum differences, which is unrelated to flooding a server.

A Distributed Denial-of-Service (DDoS) attack is defined by multiple compromised computers (a botnet) simultaneously sending traffic to a single target. The scenario describes exactly this - many hosts sending FIN packets with spoofed source IPs to exhaust the web server's connection-handling capacity. The distributed, simultaneous nature is the defining trait of DDoS over a simple DoS.

A dictionary attack is a credential-based attack that tries common passwords from a wordlist against an authentication system, not a network flooding technique.