Chapter 13: System Hardening & Security

In the realm of OS development, a system is only as strong as its weakest vulnerability. System Hardening is the process of securing a system by reducing its surface of vulnerability through the removal of unnecessary software, usernames, or facial logins, and the closing of unused ports.

1. Secure Shell (SSH) Hardening

When accessing your Termux environment remotely, default configurations are often targets for brute-force attacks. We must enforce Public Key Authentication and disable password-based logins.

# Edit the SSH configuration file
$ nano $PREFIX/etc/ssh/sshd_config

# Key Security Settings:
PasswordAuthentication no
PermitRootLogin no
PubkeyAuthentication yes

2. Network Auditing with Nmap

As an Architect, you must audit your own system to identify open ports that could serve as entry points for intruders.

# Scan your local environment for open ports
$ nmap localhost

Security Protocol: Always operate under the "Principle of Least Privilege." Never run processes with root/superuser permissions unless absolutely necessary for the task at hand.