How to Harden and Secure Linux VPS Servers Against Hacker Attacks
⚠️ Technical Alert
Symptoms Checklist
If you observe any of the following symptoms, your site or setup is affected by this issue:
- Auth logs filled with thousands of failed SSH password attempts from unknown IPs
- High CPU load spikes caused by botnets scanning server ports
- Ransomware scripts or mining files running in the background processes
- Vulnerability scan warnings regarding open databases or standard ports
Why This Happens
Linux servers are targets for automated botnets scanning the web. If you leave standard ports open or use weak passwords, bots will crack access to install scripts or steal data.
Common Underlying Causes
- Default SSH Port (22): Leaving SSH open on port 22 allows automated bot scanners to launch persistent dictionary attacks.
- Password Authentication: Relying on passwords rather than secure cryptographic SSH Key files.
- Open MySQL/Redis Ports: Leaving database ports (3306, 6379) exposed to public traffic instead of binding to localhost.
DIY Quick Fix Steps
Here is what you can check or execute immediately to troubleshoot the issue:
- Audit active connections: Run 'sudo ss -tulpn' to list all open ports on your server.
- Enable firewall: Run 'sudo ufw default deny incoming', 'sudo ufw allow ssh', and 'sudo ufw enable'.
- Modify SSH config: Set 'PasswordAuthentication no' in /etc/ssh/sshd_config to force SSH keys.
- Install Fail2ban: Run 'sudo apt install fail2ban' to automatically ban brute-force IPs.
⚠️ Caution: Changing DNS, server logs, or WordPress databases incorrectly can cause site downtime. If you're not comfortable, skip these steps and hire assistance.
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