First, Portsentry is installed on the client server, referencing our diagram above it would be the email server. There’s a minor change to the portsentry.conf, which is that it runs the client shellscript instead of the instructrouter.sh script.
This brutusclient.sh script is copied to /etc/portsentry , its only job is to SSH into the Brutus server and run instructrouter.sh from there, providing the IP address to be blocked.
This means the root account needs a public/private keypair as well, and the /root/.ssh/id-pub.rsa key needs to be copied to the server’s /root/.ssh/authorized_keys file.
If, from the client server and logged in as root, you’re able to SSH into the Brutus server as root without entering a password, you’re good to go.