Agent: Modify backdoor user PBA's commands to request for headers only

when checking for internet connection

monkey/infection_monkey/post_breach/actions/communicate_as_backdoor_user.py

@@ -67,16 +67,16 @@ class CommunicateAsBackdoorUser(PBA):
             format_string = (
                 'powershell.exe -command "[Net.ServicePointManager]::SecurityProtocol = ['
                 "Net.SecurityProtocolType]::Tls12; "
-                'Invoke-WebRequest {url} -UseBasicParsing"'
+                'Invoke-WebRequest {url} -UseBasicParsing -method HEAD"'
             )
         else:
             # if curl works, we're good.
             # If curl doesn't exist or fails and wget work, we're good.
             # And if both don't exist: we'll call it a win.
             if shutil.which("curl") is not None:
-                format_string = "curl {url}"
+                format_string = "curl {url} --head"
             else:
-                format_string = "wget -O/dev/null -q {url}"
+                format_string = "wget -O/dev/null -q {url} --method=HEAD"
         return format_string.format(url=url)
 
     def send_result_telemetry(self, exit_status, commandline, username):