out of the list under "Before you start with the test, you might be suspicious about the following:" there is only one that is important:
only interact with people using an official email address.
the rest can be used as yellow/red flags, but simply asking for confirmation via an official email address will thwart the vast majority of scams (including other ones, like someone claiming to be from Intuit calling about your QuickBooks or whatever).
> only interact with people using an official email address.
And then google whether the domain is associated with phishing attempts. i've been targeted several times recently by folks with "official" email addresses but whose domains are (per google) strongly associated with phishing.
I have seen official company recruiters operate exclusively through Gmail or whatever. Third party headhunters may not have anything tied to the sponsoring company.
It is a decent rule, but one which is immediately thwarted by companies going out of their way to constantly look illegitimate.