Boreas replaced the old alive test method, a nasl script which uses nmap. You will not see a difference when you scan a single host, but a big difference for large networks. Boreas will take always at least 5 seconds.
The main difference is that with the old classic method via host_alive_detection.nasl, the host scan must be started, the script is launched, and once the it is detected alive, the scan continue. Otherwise, the host scan finishes.
With boreas, the scanner detects first all alive hosts (quite faster than parsing and running a script) and only starts a host scan for those host which were found alive.
Also, boreas runs in parallel with the scanner. While the scanner already scans the first alive hosts found by boreas, boreas continues testing for other alive hosts in the target list.
Hi @PBSH !
Maybe the option name is a bit confusing. test_alive_hosts_only is for enabling or disabling Boreas.
Once you have selected the alive test (Boreas or classic,) the alive test will be performed with the selected method.
Boreas supports the same methods as the classic alive test. So, consider alive will scan all hosts, even those dead hosts, independently on the alive test (boreas or classic)
I hope this clarify your doubts.