CSF is generally considered an advanced firewall given it has many more configuration options than most other software firewalls (such as APF). It’s also still simple enough to install and configure, even for novice system administrators. For a simple overview on how to install and configure CSF and its security plugin LFD (Login Failure Daemon), visit our tutorial.
Let’s say that you want to check whether or not a specific IP address, maybe
csf -g 126.96.36.199
If the IP address is denied in CSF and you want to remove it, then use this command:
csf -dr 188.8.131.52
CSF then needs to be restarted for the change to take effect: