Linux Security Best Practices
- Linux Security Best Practices
This article provides a comprehensive overview of Linux security best practices for server administrators. Implementing these practices will significantly reduce the risk of compromise and ensure the integrity of your systems. This guide is geared toward newcomers to server administration and assumes a basic understanding of the Linux command line.
1. Initial Hardening
The first step in securing a Linux server is to harden it immediately after installation. This involves removing unnecessary software, configuring strong passwords, and updating the system to the latest security patches.
1.1. Package Management
Keep your system updated! Regularly update packages using your distribution's package manager. This ensures you have the latest security fixes.
| Distribution | Update Command |
|---|---|
| Debian/Ubuntu | `sudo apt update && sudo apt upgrade` |
| CentOS/RHEL/Fedora | `sudo yum update` or `sudo dnf update` |
| Arch Linux | `sudo pacman -Syu` |
1.2. User Accounts
- **Disable or Remove Unnecessary Accounts:** Remove default accounts and any accounts that are not actively used.
- **Strong Passwords:** Enforce strong password policies. Use a combination of uppercase and lowercase letters, numbers, and symbols. Consider using a password manager. See Password Management for more information.
- **Disable Root Login:** Disable direct root login via SSH. Use a regular user account with `sudo` privileges instead. Sudo Configuration details how to set this up.
- **Account Lockout:** Implement account lockout policies to prevent brute-force attacks. See Fail2ban for a common tool to assist with this.
1.3. SSH Hardening
SSH is a common target for attackers. Secure your SSH configuration:
- **Change Default Port:** Change the default SSH port (22) to a non-standard port.
- **Disable Password Authentication:** Use key-based authentication instead of password authentication. SSH Key Generation explains how to create and use SSH keys.
- **Limit User Access:** Restrict SSH access to specific users or groups.
- **Use Firewall Rules:** Configure your firewall to only allow SSH access from trusted IP addresses. See Firewall Configuration below.
2. Firewall Configuration
A firewall is essential for protecting your server. It acts as a barrier between your server and the outside world, blocking unauthorized access.
2.1. `iptables`
`iptables` is a powerful command-line firewall utility. It allows you to define rules to filter network traffic.
| Rule Type | Description |
|---|---|
| INPUT | Controls incoming traffic to the server. |
| OUTPUT | Controls outgoing traffic from the server. |
| FORWARD | Controls traffic passing *through* the server (relevant for routers). |
2.2. `firewalld`
`firewalld` is a dynamic firewall manager that provides a higher-level interface to `iptables`. It simplifies firewall configuration and management. Firewalld Configuration provides a detailed tutorial.
2.3. Basic Firewall Rules
- **Allow SSH (from trusted IPs):** Allow SSH access only from specific IP addresses.
- **Allow HTTP/HTTPS:** Allow incoming traffic on ports 80 (HTTP) and 443 (HTTPS) if you are running a web server. See Web Server Security.
- **Deny All Other Incoming Traffic:** Deny all other incoming traffic by default.
3. Intrusion Detection and Prevention
Intrusion detection and prevention systems (IDPS) can help you detect and respond to malicious activity.
3.1. Fail2ban
Fail2ban monitors log files for failed login attempts and automatically blocks the offending IP addresses. Fail2ban Configuration explains how to install and configure Fail2ban.
3.2. SELinux/AppArmor
SELinux and AppArmor are Linux security modules that provide mandatory access control (MAC). They enforce security policies that restrict the actions that processes can perform. SELinux Guide and AppArmor Guide provide detailed information on these technologies.
| Feature | SELinux | AppArmor |
|---|---|---|
| Security Model | Type Enforcement | Path-Based |
| Complexity | Generally more complex | Generally easier to configure |
| Distributions | RHEL, CentOS, Fedora | Debian, Ubuntu, SUSE |
3.3. Log Monitoring
Regularly monitor your system logs for suspicious activity. Tools like `logwatch` and `auditd` can help automate this process. See Log Analysis.
4. File Integrity Monitoring
File integrity monitoring (FIM) helps detect unauthorized changes to critical system files.
4.1. AIDE
AIDE (Advanced Intrusion Detection Environment) is a popular FIM tool. It creates a database of file attributes and then periodically checks for changes. AIDE Installation describes the installation process.
4.2. Tripwire
Tripwire is another FIM tool similar to AIDE. It can detect changes to files, directories, and other system objects.
5. Regular Security Audits
Conduct regular security audits to identify vulnerabilities and ensure that your security measures are effective. Security Audit Checklist provides a starting point.
Main Page System Administration Network Security Database Security Web Server Security Password Management Sudo Configuration Fail2ban Firewall Configuration SSH Key Generation Firewalld Configuration SELinux Guide AppArmor Guide Log Analysis AIDE Installation
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| Core i9-13900 Server (128GB) | 128 GB RAM, 2x2 TB NVMe SSD | |
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| Core i5-13500 Workstation | 64 GB DDR5 RAM, 2 NVMe SSD, NVIDIA RTX 4000 |
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| Ryzen 5 3600 Server | 64 GB RAM, 2x480 GB NVMe | CPU Benchmark: 17849 |
| Ryzen 7 7700 Server | 64 GB DDR5 RAM, 2x1 TB NVMe | CPU Benchmark: 35224 |
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