Between 20 - 30% of my Communities new users are fake / illegitimate ID's - see example's below. Is it possible to moderate new user requests or adjust security levels for new user requests.
If you wanted to do this without a plugin (though a plugin is definitely the better solution) you could add blocked domain addresses to the email regex pattern.
The portion in bold is what's new compared to our default pattern. In this case it blocks registrants from using an email domain of blockme.com OR alsoblockme.com
This option is found under Administration > Authentication > Authentication Options > Email Address Regular Expression Pattern