Linux Security Tutorials Last updated: February 7, 2025 Written by: baeldung SecuritySeries Baeldung Pro – Linux – NPI EA (cat = Baeldung on Linux) Learn through the super-clean Baeldung Pro experience: >> Membership and Baeldung Pro. No ads, dark-mode and 6 months free of IntelliJ Idea Ultimate to start with. General Core Differences Between SELinux and AppArmor How to Secure an SSH Server in Linux Set Up and Disable SELinux Capabilities of Privileged Containers in Linux How to Install Only Security Updates in Linux Test Whether a Server Is Vulnerable to Shellshock Bug Tainted Linux Kernel Preventing Bash Fork Bombs User Management Blocking Access to Particular Commands for a User in Linux Disabling Guest Sessions in Linux How to Check Whether a User's Password Is Already Set Allow Password Change That Is Similar to the Previous Password in Linux Managing Password Complexity in Linux How to Retrieve Password Expiry Time in Shell Unlocking a Linux User Account After Too Many Failed Attempts How to Disable User Logins on Linux Files and Filesystems Linux Capabilities: Setting and Modifying Permissions Check Permissions of a Mounted Filesystem in Shell Verifying if a Disk Is Encrypted in Linux Security of NFS Over Internet in Linux Set Default Permission for New Files and Subdirectories Encrypting and Decrypting Files in Linux Setting Permissions with chown and chmod Advanced File Permissions in Linux Network Communication Meaning of 169.254.169.254 on the Cloud Allowing Traffic From a Domain With Dynamic IP Address Automating ssh-copy-id Difference Between SFTP, SCP and FISH Protocols SSH Tunneling and Proxying HTTPS Connection Using Curl How to List All Connected SSH Sessions Linux Commands: Using Secure Shell (ssh) Firewalls Configuring firewalld for NFS Connections Difference Between OUTPUT and FORWARD Chains in iptables How to Allow Only SSH Access Using iptables Checking Whether a Firewall Is Running on Linux REJECT vs. DROP When Using iptables How to Use UFW (Uncomplicated Firewall) Certificates How to Add, Remove, and Update CA Certificates in Linux (popular) Conversion Between <em>.cer</em> and <em>.crt</em> How to Install Certificates in Linux CLI List All Available Certificate Authority (CA) SSL Certificates Adding a Self-Signed Certificate to the Trusted List Extracting Certificate Information with OpenSSL Configuring Automatic LetsEncrypt SSL Certificate Renewal Keys Generating Keys Without a Passphrase with OpenSSH, PuTTY, and OpenSSL SSH Key Types and Formats or How to Convert PuTTY .ppk to OpenSSH Keys Under Linux SSH Error "permissions are too open" for Private Key File Creating Public Key From Private Key How to Add Public Key to known_hosts File Generating a Key Pair via GPG Setup Public Key Authentication for SSH Generating SSH Keys in Linux What Is <em>Unlock Keyring</em> and How to Fix It (popular)