Network-centric or volume-based attacks: These overload a target network by consuming available resources with large volumes of traffic. For instance, an IP amplification denial of service (DDoS) can consume a significant amount of network capacity, resulting in slowdowns or outages. A common DDoS tactic involves sending packets to a specific host or group of hosts, overwhelming them with so much data that they cannot handle legitimate traffic.

Application Layer: Application Layer Deny of Service occurs when there is too much traffic at the application level. For instance, if you refresh a webpage repeatedly, you’re causing a Deny of Service because the server cannot handle the number of requests.

Protocol attacks: Focus on weaknesses in the underlying protocol itself rather than attacking individual hosts. For instance, an attacker could send many HTTP requests to a server, overwhelming the service’s ability to respond. Or they might exploit a weakness in the TCP/IP stack to cause a denial of service condition.

More info: The Top 5 Most Popular Method Ransomware Is Delivered And Deployed