I got several alerts in the last two days bcs our service responded 5xx in a large percentage of the requests (tipically offhours when we have zero to low traffic anyway).
When I checked the application logs I found these two;
Illegal request, responding with status ‘501 Not Implemented’: Unsupported HTTP method: MOZILLAVT
Illegal request, responding with status ‘501 Not Implemented’: Unsupported HTTP method: VTTEST
Any idea what are these, and which tools produce them? Google not helped.
It is clear that our site is under some kind of vulnerability testing, as I see the nginx access logs, but these requests are not there, which is even stranger.