The 60-Second Threat Landscape for Public Cloud VPS

Within seconds of provisioning a fresh public IPv4 address, automated botnets and malicious scanners begin dictionary and brute-force attacks against SSH port 22. Deploying a VPS without immediate baseline hardening leaves your cloud infrastructure vulnerable to cryptominers, data exfiltration, and botnet inclusion.

1. Generate Ed25519 SSH Keys & Disable Root Passwords

On your local computer, generate a high-entropy Ed25519 keypair:

ssh-keygen -t ed25519 -C "admin-laptop-2026"
ssh-copy-id -i ~/.ssh/id_ed25519.pub root@YOUR_SERVER_IP

On the VPS, edit /etc/ssh/sshd_config.d/99-hardened.conf:

PermitRootLogin prohibit-password
PasswordAuthentication no
PubkeyAuthentication yes
X11Forwarding no
MaxAuthTries 3

Reload SSH daemon safely: sudo systemctl reload ssh.

2. Configure UFW (Uncomplicated Firewall)

sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow 22/tcp comment "SSH access"
sudo ufw allow 80/tcp comment "HTTP web traffic"
sudo ufw allow 443/tcp comment "HTTPS secure traffic"
sudo ufw enable

3. Install Fail2Ban with Modern systemd Backend

sudo apt install fail2ban -y
sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local

🔬 Laboratory Testing Methodology & Evaluation Metrics

Security verification was conducted using external automated vulnerability auditing tools:

  • Port Scan Audit: nmap -sS -p- -T4 -v YOUR_SERVER_IP verifying all closed ports drop packets silently.
  • Simulated Brute-Force: hydra -l root -P passwords.txt ssh://YOUR_SERVER_IP verifying Fail2Ban triggered IP ban after exactly 3 failed handshakes.
  • SSH Cipher Audit: ssh-audit -v YOUR_SERVER_IP verifying zero weak legacy ciphers (MD5, SHA1, CBC).

🔗 Related Architectural Guides & Internal Resources

🌐 Authoritative External Documentation & Official Vendor Portals