Url_response probe is configured to monitor a set of url's and seems to be working however when servers physical access to the url's is blocked the probe does not raise an alarm.
Probe log shows
Feb 4 15:02:39:823  url_response: Using InternetConnect / HttpOpenRequest / HttpSendRequest to fetch https://www.someweb.com/
Feb 4 15:02:39:824  url_response: HttpQueryInfo returns 0 - Unknown error: 0
Feb 4 15:02:39:824  url_response: [test_url] debug - MyGet (https://www.someweb.com/) returns 0
Feb 4 15:02:39:824  url_response: [test_url] used 0 ms, 0 + 0 bytes, 0 bytes read
Feb 4 15:02:39:824  url_response: SREPLY: status = 0(OK) ->xxx.xxx.xxx.xxx/55657
The probe uses the HttpQueryInfo function when configured to use Windows NT Authentication as the authentication method.
The monitored url is returning the 0 return code to the HttpQueryInfo function
The probe interprets the 0 return code as success and thus no alarm is raised
Release : 8.51
Changing the probes configuration to Basic Authentication means the probe will use curl instead and allows the probe to successfully detect the URL status