...
Application Layer Attacks – The attackers target HTTP trying to exhaust the resource limits of Web services. Application Layer Attacks target specific Web applications flooding them with a huge quantity of requests that saturate target’s resources. Application Layer attacks are hard to detect because they don’t don’t necessarily involve large volumes of traffic and require fewer network connections with respect to other types of DDoS techniques. Some example of Application Layer DDoS attacks is Slowloris, and DDoS attacks that target Apache, Windows, or OpenBSD vulnerabilities. Application Layer Attacks magnitude is measured in Requests per second.
...