This module is a real firewall that improves the security of your site and the fight against hackers by blocking access following 3 criteria:

You can prevent Ips belonging to people or dangerous sites from accessing your site, for example an IP that spam your site by SQL injection hack or saturation attempts. Blocking IPs is very useful for blocking robots that execute automatic scripts.

The referent is the user's home domain, assuming that the user accesses your site from a forum this forum is called referent. The module also gives you the option to block referents. This feature allows you to remove external links that you deem unnecessary or dangerous (for example a hacker forum, or a scam site)

This third feature allows you to block users from one or more countries to access your site.

You can create a blacklist for all three features.

the user, referring domain and country of origin.