MoBlock is a IP blocking daemon that uses iptables. MoBlock is also unofficial PeerGuardian Linux client that is very useful in filtering malicous peers on P2P networks.
First you need [moblock http://aur.archlinux.org/packages.php?ID=5925] package from AUR. If you want GUI, install the [blockcontrol http://aur.archlinux.org/packages.php?ID=25466] (dependency for GUI) and [mobloquer http://aur.archlinux.org/packages.php?ID=14802] (moblock GUI written using Qt).
Open the /etc/moblock/config file with your favourite editor.
I recommend disabling filtering HTTP connections, so find
http https to it. It will looks like: ]
In this file you can also customize what lists MoBlock will use for filtering, but is best to keep the defaults (MoBlock will filter about 99% bad connections, but will not be too paranoid).
If you are behind NAT, add this to config:
That will whitelist everything from 192.168.0.0 to 192.168.255.255.
Now run moblock-update to update the lists.
After configuration just run
# /etc/rc.d/moblock start
This is it! If you decide that moblock must run everytime you boot up, just add word moblock to your DAEMONS array in /etc/rc.conf