This article explains how to rate limit using the recent module in IPTables.
This article explains how to secure SSH on a linux server.
This article explains how to create comments in IPTable rules.
This article explains how to create Default Blocks in IPTable rules.
This article provides 8 steps to creating a secure Linux server.
This article explains how to configure SFTP on a linux server.
This article explains how protect SSH using IP Authentication.
This article explains UFW and hows how to use it on Ubuntu.
This article explains how to configure NMAP on a linux server.