• trimstray - The Practical Linux Hardening Guide - practical step-by-step instructions for building your own hardened systems and services. Tested on CentOS 7 and RHEL 7.
• trimstray - Linux Hardening Checklist - most important hardening rules for GNU/Linux systems (summarized version of The Practical Linux Hardening Guide)
• How To Secure A Linux Server - for a single Linux server at home
• Neo23x0/auditd - Best Practice Auditd Configuration
• ANSSI - Configuration recommendations of a GNU/Linux system
• nixCraft - 40 Linux Server Hardening Security Tips (2019 edition)
• nixCraft - Tips To Protect Linux Servers Physical Console Access
• TecMint - 4 Ways to Disable Root Account in Linux
• ERNW - IPv6 Hardening Guide for Linux Servers

Red Hat Enterprise Linux - RHEL

• DISA STIGs - Red Hat Enterprise Linux 7
• nixCraft - How to set up a firewall using FirewallD on RHEL 8
• Red Hat - A Guide to Securing Red Hat Enterprise Linux 7
• Red Hat - A Guide to Securing Red Hat Enterprise Linux 7

CentOS

• Lisenet - CentOS 7 Server Hardening Guide
• HighOn.Coffee - Security Harden CentOS 7

SUSE

• SUSE Linux Enterprise Server 12 Security and Hardening Guide

Ubuntu

• Ubuntu wiki - Security Hardening Features

Ubuntu

• Awesome Windows Domain Hardening
• NSA - AppLocker Guidance - Configuration guidance for implementing application whitelisting with AppLocker
• NSA - Pass the Hash Guidance - Configuration guidance for implementing Pass-the-Hash mitigations (Archived)
• NSA - BitLocker Guidance - Configuration guidance for implementing disk encryption with BitLocker
• NSA - Event Forwarding Guidance - Configuration guidance for implementing collection of security relevant Windows Event Log events by using Windows Event Forwarding
• BSI/ERNW - Configuration Recommendations for Hardening of Windows 10 Using Built-in Functionalities - focused on Windows 10 LTSC 2019
• ACSC - Hardening Microsoft Windows 10, version 21H1, Workstations
• ACSC - Securing PowerShell in the Enterprise
• Windows Defense in Depth Strategies - work in progress
• Endpoint Isolation with the Windows Firewall - Zealand-2016/M377) talk from Ignite 2016
• ERNW - IPv6 Hardening Guide for Windows Servers
• Microsoft - How to detect, enable and disable SMBv1, SMBv2, and SMBv3 in Windows and Windows Server
• Microsoft recommended block rules - List of applications or files that can be used by an attacker to circumvent application whitelisting policies

Firewalls

• ANSSI - Recommandations de sécurité pour les architectures basées sur VMware vSphere ESXi - for VMware 5.5 (2016), in French
• ANSSI - Problématiques de sécurité associées à la virtualisation des systèmes d’information
• VMware Security Hardening Guides - covers most VMware products and versions
• DISA STIGs - Virtualisation - VMware vSphere 6.0 and 5
• ENISA - Security aspects of virtualization - generic, high-level best practices for virtualization and containers (Feb 2017)
• NIST SP 800-125 - Guide to Security for Full Virtualization Technologies - (2011)
• NIST SP 800-125B Secure Virtual Network Configuration for Virtual Machine (VM) Protection

Firewalls

• ANSSI - Recommandations de sécurité relatives au déploiement de conteneurs Docker
• How To Harden Your Docker Containers
• NIST SP 800-190 - Application Container Security Guide
• A Practical Introduction to Container Security

SSH

• ANSSI - (Open)SSH secure use recommendations
• NIST IR 7966 - Security of Interactive and Automated Access Management Using Secure Shell (SSH)
• Linux Audit - OpenSSH security and hardening
• Positron Security SSH Hardening Guides - 2018) - focused on crypto algorithms

TLS/SSL

• ANSSI - Security Recommendations for TLS - 2017, does not cover TLS 1.3
• Netherlands NCSC - IT Security Guidelines for Transport Layer Security (TLS) - 2019
• Qualys SSL Labs - SSL and TLS Deployment Best Practices - 2017, does not cover TLS 1.3
• Applied Crypto Hardening: bettercrypto.org - handy reference on how to configure the most common services’ crypto settings (TLS/SSL, PGP, SSH and other cryptographic tools)

Web Servers

• Cipherli.st - Strong Ciphers for Apache, nginx and Lighttpd
• GeekFlare - Apache Web Server Hardening and Security Guide
• Apache Config - Apache Security Hardening Guide
• Apache Tomcat 9 Security Considerations - 8.0-doc/security-howto.html) / [v7](https://tomcat.apache.org/tomcat-7.0-doc/security-howto.html)
• How to get Tomcat 9 to work with authbind to bind to port 80
• Eclipse Jetty - Configuring Security
• Jetty hardening
• CIS Microsoft IIS Benchmarks

Active Directory

• ANSSI CERT-FR - Active Directory Security Assessment Checklist - 2020 (English and French versions)

ADFS

• adsecurity.org - Securing Microsoft Active Directory Federation Server (ADFS)

LDAP

• Best Practices in LDAP Security
• LDAP: Hardening Server Security (so administrators can sleep at night)
• LDAP Authentication Best Practices - retrieved from web.archive.org
• How To Encrypt OpenLDAP Connections Using STARTTLS

DNS

• DISA STIGs - BIND 9.x

NFS

• Red Hat - RHEL7 Storage Administration Guide - Securing NFS
• NFSv4 without Kerberos and permissions - why NFSv4 without Kerberos does not provide security
• CertDepot - RHEL7: Use Kerberos to control access to NFS network shares

CUPS

• CUPS Server Security

Switches

• DISA - Layer 2 Switch SRG

Routers

• NSA - A Guide to Border Gateway Protocol (BGP) Best Practices

Firewalls

• NIST SP 800-41 Rev 1 - Guidelines on Firewalls and Firewall Policy
• trimstray - Iptables Essentials: Common Firewall Rules and Commands

CUPS

• UK NCSC - Password administration for system owners
• NIST SP 800-63 Digital Identity Guidelines
• OWASP Password Storage Cheat Sheet

CUPS

• NSA Info Sheet: UEFI Lockdown Quick Guidance (March 2018)
• NSA Tech Report: UEFI Defensive Practices Guidance (July 2017)
• ANSSI - Hardware security requirements for x86 platforms - recommendations for security features and configuration options applying to hardware devices (CPU, BIOS, UEFI, etc) (Nov 2019)

CUPS

• NSA Info Sheet: Cloud Security Basics (August 2018)
• DISA DoD Cloud Computing Security
• asecure.cloud - Build a Secure Cloud - A free repository of customizable AWS security configurations and best practices

GNU/Linux

• Lynis - script to check the configuration of Linux hosts
• OpenSCAP Base - oscap command line tool
• SCAP Workbench - GUI for oscap
• Tiger - The Unix security audit and intrusion detection tool

Windows

• PingCastle - Tool to check the security of Active Directory

TLS/SSL

• Qualys SSL Labs - List of tools to assess TLS/SSL servers and clients
• SSL Decoder - checks the SSL/TLS configuration of a server

Cloud

• DevSec Hardening Framework - a framework to automate hardening of OS and applications, using Chef, Ansible and Puppet

Windows

• mackwage/windows_hardening.cmd - Script to perform some hardening of Windows 10

TLS/SSL

• Mozilla SSL Configuration Generator

Cloud

• Vitux - 8 Ways to Generate a Random Password on Linux Shell
• SS64 - Password security and a comparison of Password Generators
• Awesome Cybersecurity Blue Team - A curated collection of awesome resources, tools, and other shiny things for cybersecurity blue teams.

Cloud

• Android Security Awesome - A collection of android security related resources.
• Awesome CTF - A curated list of CTF frameworks, libraries, resources and software.
• Awesome Hacking - A curated list of awesome Hacking tutorials, tools and resources.
• Awesome Honeypots - An awesome list of honeypot resources.
• Awesome Malware Analysis - A curated list of awesome malware analysis tools and resources.
• Awesome PCAP Tools - A collection of tools developed by other researchers in the Computer Science area to process network traces.
• Awesome Linux Containers - A curated list of awesome Linux Containers frameworks, libraries and software.
• Awesome Incident Response - A curated list of resources for incident response.
• Awesome Crypto Papers - A curated list of cryptography papers, articles, tutorials and howtos.
• Awesome Security - A collection of awesome software, libraries, documents, books, resources and cools stuffs about security.

Ubuntu

• ERNW - IPv6 Hardening Guide for OS-X