DoS attacks are categorized as what?

 DoS attacks are categorized as flood attacks or crash attacks. Flood attacks are the more common form of DoS attacks. They occur when the attacked system is overwhelmed by large amounts of traffic that the server is unable to handle. The system eventually stops. Some examples of flood attacks are ICMP flood, SYN flood, and UDP flood. Crash attacks are less frequent and they exploit flaws in the targeted system. The result is that the system crashes. Some examples of crash attacks are Ping of Death, Teardrop, and Land. References:

What is a denial-of-service (DoS) attack? | Cloudflare

What is a Denial of Service (DoS) attack? | Norton

What is a Denial of Service (DoS) Attack? | Cobalt

What is a denial of service attack (DoS) - Palo Alto Networks