- [Australian Cyber Security Center Publications](https://www.cyber.gov.au/publications)
- [FIRST Best Practice Guide Library (BPGL)](https://www.first.org/resources/guides/)
## GNU/Linux
- [ANSSI - Configuration recommendations of a GNU/Linux system](https://www.ssi.gouv.fr/en/guide/configuration-recommendations-of-a-gnulinux-system/)
- [nixCraft - 40 Linux Server Hardening Security Tips (2019 edition)](https://www.cyberciti.biz/tips/linux-security.html)
### Red Hat Enterprise Linux - RHEL
- [A Guide to Securing Red Hat Enterprise Linux 7](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html-single/security_guide/index)
### SUSE
- [SUSE Linux Enterprise Server 12 SP4 Security Guide](https://www.suse.com/documentation/sles-12/singlehtml/book_security/book_security.html)
- [NIST IR 7966 - Security of Interactive and Automated Access Management Using Secure Shell (SSH)](https://nvlpubs.nist.gov/nistpubs/ir/2015/NIST.IR.7966.pdf)
- [ANSSI - (Open)SSH secure use recommendations](https://www.ssi.gouv.fr/en/guide/openssh-secure-use-recommendations/)
- [Linux Audit - OpenSSH security and hardening](https://linux-audit.com/audit-and-harden-your-ssh-configuration/)
- [Hardentools](https://github.com/securitywithoutborders/hardentools) - for Windows individual users (not corporate environments) at risk, who might want an extra level of security at the price of some usability.