Ranjan

Quick Answer: The top 5 open-source and free Web Application Firewalls (WAF) for Linux servers in 2026 are ModSecurity (with OWASP Core Rule Set), Coraza WAF, BunkerWeb, Cloudflare Free WAF, and NAXSI. For Nginx and OpenLiteSpeed web servers, ModSecurity and Coraza offer the highest detection rates against SQL injection (SQLi), Cross-Site Scripting (XSS), and zero-day … Read more

Quick Answer: To enable Two-Factor Authentication (2FA) for SSH on Ubuntu/Debian, install libpam-google-authenticator, run google-authenticator to generate your QR code and secret key, configure /etc/pam.d/sshd with auth required pam_google_authenticator.so, update /etc/ssh/sshd_config to enable KbdInteractiveAuthentication yes, and restart OpenSSH. ⏱️ 5 min read (928 words) 🛡️ Verified on Ubuntu 24.04 / Debian 12 🔄 Updated for … Read more

Quick Answer: To protect a Linux web server from Layer 7 application-layer DDoS attacks (HTTP floods), route DNS traffic through Cloudflare Proxy (Orange Cloud) and lock down your server’s UFW firewall so that port 80 and 443 only accept connections from Cloudflare’s published IP ranges, preventing attackers from bypassing the CDN proxy. ⏱️ 5 min … Read more

Quick Answer: To scan a Linux server for malware and backdoors, install Linux Malware Detect (LMD/Maldet) paired with the ClamAV binary scanning engine. Update threat signatures with maldet -u, execute a full scan on your web directories with maldet -a /var/www/, and inspect quarantined malicious files with maldet –report. ⏱️ 5 min read (957 words) … Read more

Quick Answer: To install a free Let’s Encrypt SSL certificate on a Linux VPS, install Certbot via snap (sudo snap install –classic certbot), run the web server plugin (sudo certbot –nginx or sudo certbot –apache), enter your domain and email, and verify automated renewal with sudo certbot renew –dry-run. ⏱️ 5 min read (1,023 words) … Read more

Quick Answer: To change the default SSH port on a Linux VPS, select an unused high port (such as 22022), allow the new port in UFW (sudo ufw allow 22022/tcp), edit /etc/ssh/sshd_config to set Port 22022, restart OpenSSH (sudo systemctl restart ssh), and verify connection in a separate terminal before closing your active session. ⏱️ … Read more

Quick Answer: Install Fail2ban using sudo apt install fail2ban, create a custom configuration file at /etc/fail2ban/jail.local, enable the [sshd] jail with a 24-hour ban time (bantime = 1d), and start the service with sudo systemctl enable –now fail2ban. ⏱️ 5 min read (908 words) 🛡️ Verified on Ubuntu 24.04 / Debian 12 🔄 Updated for … Read more

Quick Answer: To secure an Ubuntu VPS using UFW (Uncomplicated Firewall), set the default policy to deny incoming traffic (sudo ufw default deny incoming), allow your SSH port (sudo ufw allow 22/tcp or sudo ufw limit ssh), allow HTTP/HTTPS (sudo ufw allow ‘Nginx Full’), and enable the firewall with sudo ufw enable. ⏱️ 5 min … Read more