According to one embodiment, an analyzer module (AM) within a same protected network and on-premise with a web application server (WAS) detects and distinguishes between types of Denial-of-Service (DoS) attacks. The AM tracks whether test HTTP messages, which include test HTTP request messages that a signal generation module (SGM) is configured to transmit to the WAS and test HTTP response messages that the WAS is expected to transmit in response to the test HTTP request messages, are timely received. The AM is aware of a timeliness that the SGM is expected to transmit the test HTTP request messages and that the WAS is expected to transmit the test response HTTP messages. The AM detects an occurrence of a DoS attack and identifies the type of the DoS attack based upon the result of the tracking indicating that a number of the test HTTP messages have not been timely received.