Temporary denial of service after failed authentication

[joseph-reynolds]

We are seeing behavior where a flood (thousands) of failed authentication requests results in the service becoming unresponsive for a few seconds. Continuing with one failed authentication per second results in the service being unresponsive for another second. This is also know as denial of service (DoS). When the bad authentication requests stop, the service returns to normal operation.
Is this behavior known? It is a defense mechanism? Just looking for information.