3 Steps to Harden Linux

Even a secure OS such as Linux can use a little hardening.

The Linux operating system has a reputation for security. However, even a secure operating system has weaknesses if not maintained properly. Linux systems have their own sets of concerns, and it is up to the user or administrator to address those concerns and close any security holes. With access to a terminal and a few commands, you can make a Linux installation even more secure than it already is.

Instructions

1. Make sure there are no extra accounts. Accounts that have no users can become a security threat if they are broken into by intruders. Look at the /etc/passwd file to see what sort of accounts exist on the system and disable them. Also, disable root login over SSH accounts by modifying the /etc/ssh/sshd_config file with the line "PermitRootLogin no."

2. Disable unneeded network services. Run the command "lsof -i" to view all active ports. Close all active ports that run services unneeded by the user or administrator (such as TCP). Also, think about running HTTP services only to close any OpenSSL library threats.

3. Maintain all security updates. Most Linux distributions release regular security updates, either on their websites or through Internet updating applications. Make sure that these are always up to date. If the system states that there are updates available, install them. Also, periodically check the distribution's update servers to see if any updates have been released.

References

• Bob Cromwell: How to Harden a Linux or OpenBSD Installation